| 1. |
- Cieslak, Anna M., et al.
(författare)
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Ultra long-lived electron-hole separation within water-soluble colloidal ZnO nanocrystals : Prospective Applications For Solar Energy Production
- 2016
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Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855. ; 30, s. 187-192
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Tidskriftsartikel (refereegranskat)abstract
- Zinc oxide was one of the first semiconductors used in dye-sensitized solar cells but its instability in aqueous media precludes its use for large-scale applications. Herein, we report on a novel ZnO nanocrystal material derived by an organometallic approach that is simultaneously stable and soluble in water due to its carboxylate oligoethylene glycol shell strongly anchored to the inorganic core by the head groups. The resulting unique inorganic core-organic shell interface also stabilizes the photo-generated hole, leading to a dramatic slowing down of charge recombination, which otherwise is a major hurdle in using nanostructured ZnO.
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| 2. |
- D'Amario, Luca, et al.
(författare)
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Chemical and Physical Reduction of High Valence Ni States in Mesoporous NiO Film for Solar Cell Application
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 9:39, s. 33470-33477
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Tidskriftsartikel (refereegranskat)abstract
- The most common material for dye-sensitized photocathodes is mesoporous NiO. We transformed the usual brownish NiO to be more transparent by reducing high valence Ni impurities. Two pretreatment methods have been used: chemical reduction by NaBH4 and thermal reduction by heating. The power conversion efficiency of the cell was increased by 33% through chemical treatment, and an increase in open-circuit voltage from 105 to 225 mV was obtained upon heat treatment. By optical spectroelectrochemistry, we could identify two species with characteristically different spectra assigned to Ni3+ and Ni4+. We suggest that the reduction of surface Ni3+ and Ni (4+) to Ni (2+) decreases the recombination reaction between holes on the NiO surface with the electrolyte. It also keeps the dye firmly on the surface, building a barrier for electrolyte recombination. This causes an increase in open-circuit photovoltage for the treated film.
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| 3. |
- D'Amario, Luca
(författare)
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Discovering Hidden Traps : in Nickel Oxide Nanoparticles for Dye-Sensitised Photocathodes
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The finite nature of fossil fuels and their effect on the global climate, raised the need to find an alternative source of energy. This source should be environment compatible, cheap and abundant. The light coming from the Sun is a promising alternative. To be fruitful, the solar energy needs to be transformed in storable and transportable energy forms like electricityor fuels. Amongst the most studied techniques dye sensitised devices offer the possibility to be designed for both the scopes: solar-to-electricity and solar-to-fuel conversions. In these applications a photocathode and a photoanode, constructed by mesoporous semisconductor films sensitised with dyes, are placed in series with one another.It follows that the photocurrent generated by one electrode should be sustained by the photocurrent produced by the other electrode. At the moment there is a substantial difference between the conversion efficiencies and the photocurrent produced by photoanodes and photocathodes. In this thesis the reasons for this discrepancy are investigated. The main responsible of the bad performance is identified in the semiconductor normally used in photocathodes, Nickel Oxide (NiO). Electrochemical impedance spectroscopy was used to elucidate the electrical properties of mesoporous NiO films. The study revealed that NiO films are able to carry a large enough current to establish that conductivity is not a limiting factor. The recombination reactions were then accused as the cause of the power losses. A time resolved spectroscopic study revealed that NiO can host two kinds of holes. One of these holes is responsible for a fast dye-NiO recombination (100 ns) and the other one for a slow recombination (10 ms). A cell featuring only the slow dye-NiO recombination would possibly reach high efficiency. The characterisation of the species associated with these two holes was performed by density-of-state assisted spectroelectrochemistry. The holes were found to be trapped by Ni2+ and Ni3+ sites located on the NiO surface forming respectively Ni3+ and Ni4+ states. A study by fs and ns transient absorption spectroscopy revealed that Ni3+ sites can trap a hole in subpicosecond time scale and this hole relaxes into a Ni2+ trap in ns timescale. The control of the Ni2+/Ni3+ratio on the NiO surface was found to be crucial for a high cell photovoltage. In the thesis these results are discussed and used to propose an explanation and some solutions to the poor performance of NiO-based dye sensitised cells.
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| 4. |
- D'Amario, Luca, et al.
(författare)
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Kinetic Evidence of Two Pathways for Charge Recombination in NiO-Based Dye-Sensitized Solar Cells
- 2015
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 6:5, s. 779-783
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Tidskriftsartikel (refereegranskat)abstract
- Mesoporous nickel oxide has been used as electrode material for p-type dye-sensitized solar cells (DSCs) for many years but no high efficiency cells have yet been obtained. One of the main issues that lowers the efficiency is the poor fill factor, for which a clear reason is still missing. In this paper we present the first evidence for a relation between applied potential and the charge recombination rate of the NiO electrode. In particular, we find biphasic recombination kinetics: a fast (15 ns) pathway attributed to the reaction with the holes in the valence band and a slow (1 ms) pathway assigned to the holes in the trap states. The fast component is the most relevant at positive potentials, while the slow component becomes more important at negative potentials. This means that at the working condition of the cell, the fast recombination is the most important. This could explain the low fill factor of NiO-based DSCs.
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| 5. |
- D'Amario, Luca, et al.
(författare)
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Towards time resolved characterization of electrochemical reactions : electrochemically-induced Raman spectroscopy
- 2022
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Ingår i: Chemical Science. - : RSC Publishing. - 2041-6520 .- 2041-6539. ; 13:36, s. 10734-10742
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Tidskriftsartikel (refereegranskat)abstract
- Structural characterization of transient electrochemical species in the sub-millisecond time scale is the all-time wish of any electrochemist. Presently, common time resolution of structural spectro-electrochemical methods is about 0.1 seconds. Herein, a transient spectro-electrochemical Raman setup of easy implementation is described which allows sub-ms time resolution. The technique studies electrochemical processes by initiating the reaction with an electric potential (or current) pulse and analyses the product with a synchronized laser pulse of the modified Raman spectrometer. The approach was validated by studying a known redox driven isomerization of a Ru-based molecular switch grafted, as monolayer, on a SERS active Au microelectrode. Density-functional-theory calculations confirmed the spectral assignments to sub-ms transient species. This study paves the way to a new generation of time-resolved spectro-electrochemical techniques which will be of fundamental help in the development of next generation electrolizers, fuel cells and batteries.
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| 6. |
- D'Amario, Luca, et al.
(författare)
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Tuning of Conductivity and Density of States of NiO Mesoporous Films Used in p-Type DSSCs
- 2014
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:34, s. 19556-19564
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Tidskriftsartikel (refereegranskat)abstract
- Nickel oxide has been used as the mesoporous electrode material for p-type dye sensitized solar cell (DSSC) for many years, but no high efficiency cells have been obtained yet. The poor results are commonly attributed to the lack of conductivity of the NiO film. In this paper we studied the electrical conduction of NiO mesoporous film with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). We used unsensitized NiO on FTO as an electrode with no dye adsorbed on the surface. Tests made with a DSSC device-like cell (FTO-Pt-I-/I-3(-)-NiO-FTO) showed a surprisingly high Faradaic current (20 mA/cm(-2) at 1 V), proving a good electrical conductivity of mesoporous NiO. We also used lithium as dopant to improve the electrical properties of the film. The Li-doping resulted in widening the inert (not conductive) window in the CV plot. The EIS analysis clarified that this behavior is due to a strong dependence of the valence band shape and position with respect to the Li-doping concentration. Our results show that DSSC performance does not need to be limited by the conductivity of mesoporous NiO, which encourages more effort in p-type DSSC research based on this material.
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| 7. |
- D'Amario, Luca, 1986-, et al.
(författare)
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Unveiling hole trapping and surface dynamics of NiO nanoparticles
- 2018
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Ingår i: Chemical Science. - 2041-6520 .- 2041-6539. ; 9:1, s. 223-230
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Tidskriftsartikel (refereegranskat)abstract
- The research effort in mesoporous p-type semiconductors is increasing due to their potential application in photoelectrochemical energy conversion devices. In this paper an electron-hole pair is created by band-gap excitation of NiO nanoparticles and the dynamics of the electron and the hole is followed until their recombination. By spectroscopic characterization it was found that surface Ni3+ states work as traps for both electrons and holes. The trapped electron was assigned to a N2+ state and the trapped hole to a Ni4+ state. The recombination kinetics of these traps was studied and related with the concept of hole relaxation suggested before.The timescale of the hole relaxation was foundto be in the order of tens of ns. Finally the spectrosc opic evidence of this relaxation is presented in a sensitized film.
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| 8. |
- Freitag, Marina, et al.
(författare)
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Supramolecular Hemicage Cobalt Mediators for Dye-Sensitized Solar Cells
- 2016
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Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 17:23, s. 3845-3852
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Tidskriftsartikel (refereegranskat)abstract
- A new class of dye-sensitized solar cells (DSSCs) using the hemicage cobalt-based mediator [Co(ttb)](2+/3+) with the highly preorganized hexadentate ligand 5,5 '', 5 ''''-((2,4,6-triethyl benzene-1,3,5-triyl)tris(ethane-2,1-diyl))tri-2,2'-bipyridine (ttb) has been fully investigated. The performances of DSSCs sensitized with organic D-p-A dyes utilizing either [Co(ttb)](2+/3+) or the conventional [Co(bpy)(3)](2+/3+) (bpy = 2,2'-bipyridine) redox mediator are comparable under 1000 Wm(-2) AM 1.5 G illumination. However, the hemicage complexes exhibit exceptional stability under thermal and light stress. In particular, a 120-hour continuous light illumination stability test for DSSCs using [Co(ttb)](2+/3+) resulted in a 10% increase in the performance, whereas a 40% decrease in performance was found for [Co(bpy)(3)](2+/3+) electrolyte-based DSSCs under the same conditions. These results demonstrate the great promise of [Co(ttb)](2+/3+) complexes as redox mediators for efficient, cost-effective, large-scale DSSC devices.
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| 9. |
- Freys, Jonathan C., et al.
(författare)
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Ru-based donor-acceptor photosensitizer that retards charge recombination in a p-type dye-sensitized solar cell
- 2012
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 41:42, s. 13105-13111
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis and characterization of a donor-acceptor ruthenium polypyridyl complex as a photosensitizer for p-type dye-sensitized solar cells (DSSCs). The electrochemical, photophysical, and photovoltaic performance of two ruthenium-based photosensitizers were tested in NiO-based DSSCs; bis-(2,2′-bipyridine-4,4′-dicarboxylic acid) 2N-(1,10-phenanthroline)-4-nitronaphthalene-1,8-dicarboximide ruthenium(ii), ([Ru(dcb) 2(NMI-phen)](PF 6) 2) and tris-(2,2′-bipyridine-4,4′-dicarboxylic acid) 3 ruthenium(ii), [(Ru(dcb) 3)Cl 2]. The presence of an electron-accepting group, 4-nitronaphthalene-1,8-dicarboximide (NMI), attached to the phenanthroline of [Ru(dcb) 2(NMI-phen)] 2+ resulted in long-lived charge separation between reduced [Ru(dcb) 2(NMI-phen)] 2+ and NiO valence band holes; 10-50 μs. In the reduced state for [Ru(dcb) 2(NMI-phen)] 2+, the electron localized on the distal NMI group. In tests with I 3 -/I - and Co(4,4′-di-tert-butyl-bipyridine) 3 2+/3+ electrolytes, [Ru(dcb) 2(NMI-phen)] 2+ outperformed [Ru(dcb) 3] 2+ in solar cell efficiency in devices. A record APCE (25%) was achieved for a ruthenium photosensitizer in a p-type DSSC. Insights on photosensitizer regeneration kinetics are included.
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| 10. |
- Gao, Jiajia, et al.
(författare)
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Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells : An Electrolyte Effect
- 2018
-
Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 10:31, s. 26241-26247
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Tidskriftsartikel (refereegranskat)abstract
- A significant increase in the photocurrent generation during light soaking for solar cells sensitized by the triphenylamine-based D-pi-A organic dyes (PD2 and LEG1) and mediated by cobalt bipyridine redox complexes has been observed and investigated. The crucial role of the electrolyte has been identified in the performance improvement. Control experiments based on a pretreatment strategy reveals TBP as the origin. The increase in the current and IPCE has been interpreted by the interfacial charge-transfer kinetics studies. A slow component in the injection kinetics was exposed for this system. This change explains the increase in the electron lifetime and collection efficiency. Photoelectron spectroscopic measurements show energy shifts at the dye/TiO2 interface, leading us to formulate a hypothesis with respect to an electrolyte induced dye reorganization at the surface.
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| 11. |
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| 12. |
- Jiang, Shan, et al.
(författare)
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Copper Carbonate Hydroxide as Precursor of Interfacial CO in CO2 Electroreduction
- 2022
-
Ingår i: ChemSusChem. - : John Wiley & Sons. - 1864-5631 .- 1864-564X. ; 15:8
-
Tidskriftsartikel (refereegranskat)abstract
- Copper electrodes are especially effective in catalysis of C-2 and further multi-carbon products in the CO2 reduction reaction (CO2RR) and therefore of major technological interest. The reasons for the unparalleled Cu performance in CO2RR are insufficiently understood. Here, the electrode-electrolyte interface was highlighted as a dynamic physical-chemical system and determinant of catalytic events. Exploiting the intrinsic surface-enhanced Raman effect of previously characterized Cu foam electrodes, operando Raman experiments were used to interrogate structures and molecular interactions at the electrode-electrolyte interface at subcatalytic and catalytic potentials. Formation of a copper carbonate hydroxide (CuCarHyd) was detected, which resembles the mineral malachite. Its carbonate ions could be directly converted to CO at low overpotential. These and further experiments suggested a basic mode of CO2/carbonate reduction at Cu electrodes interfaces that contrasted previous mechanistic models: the starting point in carbon reduction was not CO2 but carbonate ions bound to the metallic Cu electrode in form of CuCarHyd structures. It was hypothesized that Cu oxides residues could enhance CO2RR indirectly by supporting formation of CuCarHyd motifs. The presence of CuCarHyd patches at catalytic potentials might result from alkalization in conjunction with local electrical potential gradients, enabling the formation of metastable CuCarHyd motifs over a large range of potentials.
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| 13. |
- Liu, Si, et al.
(författare)
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Electrocatalytic Water Oxidation at Neutral pH–Deciphering the Rate Constraints for an Amorphous Cobalt‐Phosphate Catalyst System
- 2022
-
Ingår i: Advanced Energy Materials. - : Wiley-VCH Verlagsgesellschaft. - 1614-6832 .- 1614-6840. ; 12:46
-
Tidskriftsartikel (refereegranskat)abstract
- The oxygen evolution reaction (OER) is pivotal in sustainable fuel production. Neutral-pH OER reduces operational risks and enables direct coupling to electrochemical CO2 reduction, but typically is hampered by low current densities. Here, the rate limitations in neutral-pH OER are clarified. Using cobalt-based catalyst films and phosphate ions as essential electrolyte bases, current–potential curves are recorded and simulated. Operando X-ray spectroscopy shows the potential-dependent structural changes independent of the electrolyte phosphate concentration. Operando Raman spectroscopy uncovers electrolyte acidification at a micrometer distance from the catalyst surface, limiting the Tafel slope regime to low current densities. The electrolyte proton transport is facilitated by diffusion of either phosphate ions (base pathway) or H3O+ ions (water pathway). The water pathway is not associated with an absolute current limit but is energetically inefficient due to the Tafel-slope increase by 60 mV dec−1, shown by an uncomplicated mathematical model. The base pathway is a specific requirement in neutral-pH OER and can support high current densities, but only with accelerated buffer-base diffusion. Catalyst internal phosphate diffusion or other internal transport mechanisms do not limit the current densities. A proof-of-principle experiment shows that current densities exceeding 1 A cm−2 can also be achieved in neutral-pH OER.
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| 14. |
- Liu, Si, et al.
(författare)
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Selected applications of operando Raman spectroscopy in electrocatalysis research
- 2022
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Ingår i: Current Opinion in Electrochemistry. - : Elsevier. - 2451-9103. ; 35
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Forskningsöversikt (refereegranskat)abstract
- Knowledge-guided improvement of electrocatalytic materials is facilitated by insight in determinants of activity, selectivity, and stability. Catalyst re-construction, surface adsorbates and reaction intermediates, and the mechanistic role of the electrolyte can be addressed by operando (= in situ) Raman spectroscopy, where Raman scattering is detected during electrochemical operation. After outlining the basic experimental technology and addressing the light-damage problem, selected applications in electrocatalysis research are reviewed: (1) Redox-state changes of the catalyst material induced by electrode potentials are traced by operando Raman spectroscopy. (2) Surface-bound (adsorbed) educt, products and reaction intermediates are detected using surface-enhanced Raman spectroscopy (SERS). (3) Local-pH values are determined at the catalyst-electrolyte interface, with spatial resolution at the visible-light diffraction limit.
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| 15. |
- Nappini, S., et al.
(författare)
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Soft x-ray spectroscopies in liquids and at solid-liquid interface at BACH beamline at Elettra
- 2021
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 92:1
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Tidskriftsartikel (refereegranskat)abstract
- The beamline for advanced dichroism of the Istituto Officina dei Materiali-Consiglio Nazionale delle Ricerche, operating at the Elettra synchrotron in Trieste (Italy), works in the extreme ultraviolet-soft x-ray photon energy range with selectable light polarization, high energy resolution, brilliance, and time resolution. The beamline offers a multi-technique approach for the investigation of the electronic, chemical, structural, magnetic, and dynamical properties of materials. Recently, one of the three end stations has been dedicated to experiments based on electron transfer processes at the solid/liquid interfaces and during photocatalytic or electrochemical reactions. Suitable cells to perform soft x-ray spectroscopy in the presence of liquids and reagent gases at ambient pressure were developed. Here, we present two types of static cells working in transmission or in fluorescence yield and an electrochemical flow cell that allows us to carry out cyclic voltammetry in situ and electrodeposition on a working electrode and to study chemical reactions under operando conditions. Examples of x-ray absorption spectroscopy measurements performed under ambient conditions and during electrochemical experiments in liquids are presented.
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| 16. |
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| 17. |
- Pasquini, Chiara, et al.
(författare)
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Operando tracking of oxidation-state changes by coupling electrochemistry with time-resolved X-ray absorption spectroscopy demonstrated for water oxidation by a cobalt-based catalyst film
- 2021
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Nature. - 1618-2642 .- 1618-2650. ; 413:21, s. 5395-5408
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Tidskriftsartikel (refereegranskat)abstract
- Transition metal oxides are promising electrocatalysts for water oxidation, i.e., the oxygen evolution reaction (OER), which is critical in electrochemical production of non-fossil fuels. The involvement of oxidation state changes of the metal in OER electrocatalysis is increasingly recognized in the literature. Tracing these oxidation states under operation conditions could provide relevant information for performance optimization and development of durable catalysts, but further methodical developments are needed. Here, we propose a strategy to use single-energy X-ray absorption spectroscopy for monitoring metal oxidation-state changes during OER operation with millisecond time resolution. The procedure to obtain time-resolved oxidation state values, using two calibration curves, is explained in detail. We demonstrate the significance of this approach as well as possible sources of data misinterpretation. We conclude that the combination of X-ray absorption spectroscopy with electrochemical techniques allows us to investigate the kinetics of redox transitions and to distinguish the catalytic current from the redox current. Tracking of the oxidation state changes of Co ions in electrodeposited oxide films during cyclic voltammetry in neutral pH electrolyte serves as a proof of principle.
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| 18. |
- Shylin, Sergii I., et al.
(författare)
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Efficient visible light-driven water oxidation catalysed by an iron(IV) clathrochelate complex
- 2019
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Ingår i: Chemical Communications. - 1359-7345 .- 1364-548X. ; 55:23, s. 3335-3338
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Tidskriftsartikel (refereegranskat)abstract
- A water-stable FeIV clathrochelate complex catalyzes fast and homogeneous photochemical oxidation of water to dioxygen with a turnover frequency of 2.27 s−1 and a maximum turnover number of 365. An FeV intermediate generated under catalytic conditions is trapped and characterised using EPR and Mössbauer spectroscopy.
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| 19. |
- Shylin, Sergii I., et al.
(författare)
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Photoinduced hole transfer from tris(bipyridine)ruthenium dye to a high-valent iron-based water oxidation catalyst
- 2019
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Ingår i: Faraday discussions. - : ROYAL SOC CHEMISTRY. - 1359-6640 .- 1364-5498. ; 215, s. 162-174
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Tidskriftsartikel (refereegranskat)abstract
- An efficient water oxidation system is a prerequisite for developing solar energy conversion devices. Using advanced time-resolved spectroscopy, we study the initial catalytic relevant electron transfer events in the light-driven water oxidation system utilizing [Ru(bpy)(3)](2+) (bpy = 2,2 '-bipyridine) as a light harvester, persulfate as a sacrificial electron acceptor, and a high-valent iron clathrochelate complex as a catalyst. Upon irradiation by visible light, the excited state of the ruthenium dye is quenched by persulfate to afford a [Ru(bpy)(3)](3+)/SO4- pair, showing a cage escape yield up to 75%. This is followed by the subsequent fast hole transfer from [Ru(bpy)(3)](3+) to the Fe-IV catalyst to give the long-lived Fe-V intermediate in aqueous solution. In the presence of excess photosensitizer, this process exhibits pseudo-first order kinetics with respect to the catalyst with a rate constant of 3.2(1) x 10(10) s(-1). Consequently, efficient hole scavenging activity of the high-valent iron complex is proposed to explain its high catalytic performance for water oxidation.
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| 20. |
- Singh, Suryansh, et al.
(författare)
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Coherent Acoustic Interferometry during the Photodriven Oxygen Evolution Reaction Associates Strain Fields with the Reactive Oxygen Intermediate (Ti-OH*)
- 2021
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 143:39, s. 15984-15997
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Tidskriftsartikel (refereegranskat)abstract
- The oxygen evolution reaction (OER) from water requires the formation of metastable, reactive oxygen intermediates to enable oxygen-oxygen bond formation. Conversely, such reactive intermediates could also structurally modify the catalyst. A descriptor for the overall catalytic activity, the first electron and proton transfer OER intermediate from water, (M-OH*), has been associated with significant distortions of the metal-oxygen bonds upon chargetrapping. Time-resolved spectroscopy of in situ, photodriven OER on transition metal oxide surfaces has characterized M-OH* for the charge trapping and the symmetry of the lattice distortions by optical and vibrational transitions, respectively, but had yet to detect an interfacial strain field arising from a surface coverage M-OH*. Here, we utilize picosecond, coherent acoustic interferometry to detect the uniaxial strain normal to the SrTiO3/aqueous interface directly caused by Ti-OH*. The spectral analysis applies a fairly general methodology for detecting a combination of the spatial extent, magnitude, and generation time of the interfacial strain through the coherent oscillations' phase. For lightly n-doped SrTiO3, we identify the strain generation time (1.31 ps), which occurs simultaneously with Ti-OH* formation, and a tensile strain of 0.06% (upper limit 0.6%). In addition to fully characterizing this intermediate across visible, mid-infrared, and now GHz-THz probes on SrTiO3, we show that strain fields occur with the creation of some M-OH*, which modifies design strategies for tuning catalytic activity and provides insight into photo-induced degradation so prevalent for OER. To that end, the work put forth here provides a unique methodology to characterize intermediate-induced interfacial strain across OER catalysts.
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| 21. |
- Spallacci, Claudia, et al.
(författare)
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Fabricating high-purity graphite disk electrodes as a cost-effective alternative in fundamental electrochemistry research
- 2024
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Graphite electrodes offer remarkable electrochemical properties, emerging as a viable alternative to glassy carbon (GCE) and other carbon-based electrodes for fundamental electrochemistry research. We report the fabrication and characterization of high-purity graphite disk electrodes (GDEs), made from cost-effective materials and a solvent-free methodology employing readily available laboratory equipment. Analysis of their physical properties via SEM, EDX and XPS reveals no metallic interferences and a notably high porosity, emphasizing their potential. The electrochemical performances of GDEs were found to be comparable to those of GCE. Immobilization of peptides and enzymes, both via covalent coupling and surface adsorption, was used to explore potential applications of GDEs in bioelectrochemistry. Enzyme activity could be addressed both via direct electron transfer and mediated electron transfer mechanism. These results highlight the interesting properties of our GDEs and make them a low-cost alternative to other carbon-based electrodes, with potential for future real-world applications.
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| 22. |
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| 23. |
- Tian, Lei, et al.
(författare)
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Understanding the Role of Surface States on Mesoporous NiO Films
- 2020
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 142:43
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Tidskriftsartikel (refereegranskat)abstract
- Surface states of mesoporous NiO semiconductor films have particular properties differing from the bulk and are able to dramatically influence the interfacial electron transfer and adsorption of chemical species. To achieve a better performance of NiO-based p-type dye-sensitized solar cells (p-DSCs), the function of the surface states has to be understood. In this paper, we applied a modified atomic layer deposition procedure that is able to passivate 72% of the surface states on NiO by depositing a monolayer of Al2O3. This provides us with representative control samples to study the functions of the surface states on NiO films. A main conclusion is that surface states, rather than the bulk, are mainly responsible for the conductivity in mesoporous NiO films. Furthermore, surface states significantly affect dye regeneration (with I–/I3– as redox couple) and hole transport in NiO-based p-DSCs. A new dye regeneration mechanism is proposed in which electrons are transferred from reduced dye molecules to intra-bandgap states, and then to I3– species. The intra-bandgap states here act as catalysts to assist I3– reduction. A more complete mechanism is suggested to understand the particular hole transport behavior in p-DSCs, in which the hole transport time is independent of light intensity. This is ascribed to the percolation hole hopping on the surface states. When the concentration of surface states was significantly reduced, the light-independent charge transport behavior in pristine NiO-based p-DSCs transformed into having an exponential dependence on light intensity, similar to that observed in TiO2-based n-type DSCs. These conclusions on the function of surface states provide new insight into the electronic properties of mesoporous NiO films.
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| 24. |
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| 25. |
- Wood, Christopher J., et al.
(författare)
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A comprehensive comparison of dye-sensitized NiO photocathodes for solar energy conversion
- 2016
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 18:16, s. 10727-10738
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Tidskriftsartikel (refereegranskat)abstract
- We investigated a range of different mesoporous NiO electrodes prepared by different research groups and private firms in Europe to determine the parameters which influence good quality photoelectrochemical devices. This benchmarking study aims to solve some of the discrepancies in the literature regarding the performance of p-DSCs due to differences in the quality of the device fabrication. The information obtained will lay the foundation for future photocatalytic systems based on sensitized NiO so that new dyes and catalysts can be tested with a standardized material. The textural and electrochemical properties of the semiconducting material are key to the performance of photocathodes. We found that both commercial and non-commercial NiO gave promising solar cell and water-splitting devices. The NiO samples which had the two highest solar cell efficiency (0.145% and 0.089%) also gave the best overall theoretical H-2 conversion.
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