| 1. |
- Aftab, Umair, et al.
(författare)
-
Two step synthesis of TiO2–Co3O4 composite for efficient oxygen evolution reaction
- 2021
-
Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 46:13, s. 9110-9122
-
Tidskriftsartikel (refereegranskat)abstract
- For an active hydrogen gas generation through water dissociation, the sluggish oxygen evolution reaction (OER) kinetics due to large overpotential is a main hindrance. Herein, a simple approach is used to produce composite material based on TiO2/Co3O4 for efficient OER and overpotential is linearly reduced with increasing amount of TiO2. The scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) investigations reveal the wire like morphology of composite materials, formed by the self-assembly of nanoparticles. The titania nanoparticles were homogenously distributed on the larger Co3O4 nanoparticles. The powder x-ray diffraction revealed a tetragonal phase of TiO2 and the cubic phase of Co3O4 in the composite materials. Composite samples with increasing TiO2 content were obtained (18%, 33%, 41% and 65% wt.). Among the composites, cobalt oxide-titanium oxide with the highest TiO2 content (CT-20) possesses the lowest overpotential for OER with a Tafel slope of 60 mV dec−1 and an exchange current density of 2.98 × 10−3A/cm2. The CT-20 is highly durable for 45 h at different current densities of 10, 20 and 30 mA/cm2. Electrochemical impedance spectroscopy (EIS) confirmed the fast charge transport for the CT-20 sample, which potentially accelerated the OER kinetics. These results based on a two-step methodology for the synthesis of TiO2/Co3O4 material can be useful and interesting for various energy storage and energy conversion systems.
|
|
| 2. |
- Bhatti, Adeel Liaquat, et al.
(författare)
-
Nanostructured Co3O4 electrocatalyst for OER : The role of organic polyelectrolytes as soft templates
- 2021
-
Ingår i: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 398
-
Tidskriftsartikel (refereegranskat)abstract
- Designing an efficient electrocatalyst for the oxygen evolution reaction (OER) in alkaline media is highly needed but very challenging task. Herein, we used organic polyelectrolytes such as (carboxymethyl cellulose) CMC and polyacrylamide polymers for the growth of Co3O4 nanostructures by aqueous chemical growth method. The morphology and composition studies were performed on scanning electron microscopy (SEM), energy dispersive X-ray (EDX), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) techniques. The structural properties and the surface chemistry of the Co3O4 electrocatalysts were correlated to the OER performance, and the enhancement mechanism with respect to pristine Co3O4 was observed to be specifically related to the polyelectrolyte templating role.Co3O4@CMC composites displayed reduced crystallite size, producing OER overpotential as low as 290 mV at 10 mAcm−2 in 1.0 KOH and Tafel slope of 71 mVdec−1, suggesting fast transfer of intermediates and electrons during water electrolysis. On the other hand, the use of polyacrylamide and its different templating mechanism resulted in similar crystallite size, but preferential exposed faces and larger surface vacancies content, as demonstrated by HR-TEM and XPS, respectively. Consistently, this material displays cutting-edge OER performance, such as overpotential of 260 mV at 10 mAcm−2 and a low Tafel slope of 63 mVdec−1. The proposed strategy for the preparation of Co3O4 nanostructures in the presence of CMC and polyacrylamide is facile, mass production, thus it could equally contributed towards the realization of hydrogen energy. Therefore, these nanostructures of Co3O4 can be regarded as an alternative and promising materials for the different electrochemical applications including fuel cells, metal air batteries, overall water electrolysis and other energy storage devices.
|
|
| 3. |
- Infantes-Molina, Antonia, et al.
(författare)
-
Au-Decorated Ce–Ti Mixed Oxides for Efficient CO Preferential Photooxidation
- 2020
-
Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:34, s. 38019-38030
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated the photocatalytic behavior of gold nanoparticles supported on CeO2–TiO2 nanostructured matrixes in the CO preferential oxidation in H2-rich stream (photo-CO-PROX), by modifying the electronic band structure of ceria through addition of titania and making it more suitable for interacting with free electrons excited in gold nanoparticles through surface plasmon resonance. CeO2 samples with different TiO2 concentrations (0–20 wt %) were prepared through a slow coprecipitation method in alkaline conditions. The synthetic route is surfactant-free and environmentally friendly. Au nanoparticles (<1.0 wt % loading) were deposited on the surface of the CeO2–TiO2 oxides by deposition–precipitation. A benchmarking sample was also considered, prepared by standard fast coprecipitation, to assess how a peculiar morphology can affect the photocatalytic behavior. The samples appeared organized in a hierarchical needle-like structure, with different morphologies depending on the Ti content and preparation method, with homogeneously distributed Au nanoparticles decorating the Ce–Ti mixed oxides. The morphology influences the preferential photooxidation of CO to CO2 in excess of H2 under simulated solar light irradiation at room temperature and atmospheric pressure. The Au/CeO2–TiO2 systems exhibit much higher activity compared to a benchmark sample with a non-organized structure. The most efficient sample exhibited CO conversions of 52.9 and 80.2%, and CO2 selectivities equal to 95.3 and 59.4%, in the dark and under simulated sunlight, respectively. A clear morphology–functionality correlation was found in our systematic analysis, with CO conversion maximized for a TiO2 content equal to 15 wt %. The outcomes of this study are significant advancements toward the development of an effective strategy for exploitation of hydrogen as a viable clean fuel in stationary, automotive, and portable power generators.
|
|
| 4. |
- Landström, Anton, et al.
(författare)
-
Reduced graphene oxide-ZnO hybrid composites as photocatalysts : The role of nature of the molecular target in catalytic performance
- 2021
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 47:14, s. 19346-19355
-
Tidskriftsartikel (refereegranskat)abstract
- Spurred by controversial literature findings, we enwrapped reduced graphene oxide (rGO) in ZnO hierarchical microstructures (rGO loadings spanning from 0.01 to 2 wt%) using an in situ synthetic procedure. The obtained hybrid composites were carefully characterized, aiming at shining light on the possible role of rGO on the claimed increased performance as photocatalysts. Several characterization tools were exploited to unveil the effect exerted by rGO, including steady state and time resolved photoluminescence, electron microscopies and electrochemical techniques, in order to evaluate the physical, optical and electrical features involved in determining the catalytic degradation of rhodamine B and phenol in water.Several properties of native ZnO structures were found changed upon the rGO enwrapping (including optical absorbance, concentration of native defects in the ZnO matrix and double-layer capacitance), which are all involved in determining the photocatalytic performance of the hybrid composites. The findings discussed in the present work highlight the high complexity of the field of application of graphene-derivatives as supporters of semiconducting metal oxides functionality, which has to be analyzed through a multi-parametric approach.
|
|
| 5. |
- Mazzaro, Raffaello, et al.
(författare)
-
Hybrid Silicon Nanocrystals for Color-Neutral and Transparent Luminescent Solar Concentrators
- 2019
-
Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 6:9, s. 2303-2311
-
Tidskriftsartikel (refereegranskat)abstract
- One of the most detrimental loss mechanisms in Luminescent Solar Concentrators (LSCs) is reabsorption of emitted light from the luminophore. Silicon Nanocrystals (SiNCs) offer a solution due to the high apparent Stokes shift, but the poor absorption properties limit their performance as LSC luminophores. Coupling an organic dye to SiNCs represents a smart approach to obtain sensitization of SiNC luminescence by the organic dyes, thus, resulting in tunable and improved optical properties of LSCs. In particular, 9,10-diphenylanthracene was employed as a UV sensitizer for SiNCs in order to produce LSCs with an aesthetic appearance suitable to smart window application and optical efficiency as high as 4.25%. In addition, the role of the energy transfer process on LSC performance was elucidated by a thorough optical and photovoltaic characterization.
|
|
| 6. |
- Shifa, Tofik Ahmed, et al.
(författare)
-
In Situ-Generated Oxide in Sn-Doped Nickel Phosphide Enables Ultrafast Oxygen Evolution
- 2021
-
Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 11:8, s. 4520-4529
-
Tidskriftsartikel (refereegranskat)abstract
- Water splitting is considered one of the most promising approaches to power the globe without the risk of environmental pollution. The oxygen evolution reaction (OER) is even more challenging because the generation of only one oxygen molecule involves the transfer of four e– and removal of four H+ ions from water. Thus, developing highly efficient catalysts to meet industrial requirements remains a focus of attention. Herein, the prominent role of Sn in accelerating the electron transfer kinetics of Ni5P4 nanosheets in OER is reported. The post catalytic survey elucidates that the electrochemically induced Ni–Sn oxides at the vicinity of phosphides are responsible for the observed catalytic activity, delivering current densities of 10, 30, and 100 mA cm–2 at overpotentials of only 173 ± 5.2, 200 ±7.4, and 310 ± 5.5 mV, respectively. The density functional theory calculation also supports the experimental findings from the basis of the difference observed in density of states at the Fermi level in the presence/absence of Sn. This work underscores the role of Sn in OER and opens a promising avenue toward practical implementation of hydrogen production through water splitting and other catalytic reactions.
|
|
| 7. |
- Shifa, Tofik Ahmed, et al.
(författare)
-
Interfacing CrOx and CuS for synergistically enhanced water oxidation catalysis
- 2023
-
Ingår i: Chemical Engineering Journal. - : Elsevier B.V.. - 1385-8947 .- 1873-3212. ; 453:Part 1
-
Tidskriftsartikel (refereegranskat)abstract
- The sluggish kinetics associated with the oxygen evolution reaction (OER) limits the sustainability of fuel production and chemical synthesis. Developing catalysts based on Earth abundant elements with a reasonable strategy could solve the challenge. Here, we present a heterostructure built from CrOx and CuS whose interface gives rise to the advent of new functionalities in catalytic activity. Using X-ray photoelectron and absorption spectroscopies, we identified the multiple oxidation states and low coordination number of Cr metal in CrOx-CuS heterostructure. Benefitting from these features, CrOx-CuS generates oxygen gas through water splitting with a low over potential of 190 mV vs RHE at a current density of 10 mA cm−2. The catalyst shows no evident deactivation after a 36-hours operation in alkaline medium. The high catalytic activity, inspired by first principles calculations, and long-time durability make it one of the most effective OER electrocatalysts.
|
|
| 8. |
- Taranova, Anastasiia, et al.
(författare)
-
Nickel and Cobalt Selenite Hydrates as Broad Solar Absorbers for Enhanced Solar Water Evaporation
- 2024
-
Ingår i: Solar RRL. - : John Wiley and Sons Inc. - 2367-198X.
-
Tidskriftsartikel (refereegranskat)abstract
- Inorganic black materials possessing hydrophilicity are scarce but can be of great importance in areas such as solar water evaporation and solar steam generation. Herein, for the first time, transition-metal selenite hydrates (specifically, Earth-abundant metals Ni and Co) not only possess high solar absorbance (>96 %) in the solar spectral range (UV–vis–NIR) but also excellent hydrophilicity, which plays a key role in water transport in the solar steam generation. The hydrophilic behavior in selenite hydrates originates from trapped “water of hydration” inside its crystal lattice, which can easily form hydrogen bonds with other water molecules, facilitating water transport. Owing to the abovementioned properties, the studied selenite hydrates are tested for solar water evaporation, showing excellent water evaporation rates of 1.83 and 2.34 kg m−2 h−1 for nickel selenite hydrate and cobalt selenite hydrate, exceeding the theoretical limit of 1.47 kg m−2 h−1.
|
|
| 9. |
- Taranova, Anastasiia, et al.
(författare)
-
Unraveling the optoelectronic properties of CoSbx intrinsic selective solar absorber towards high-temperature surfaces
- 2023
-
Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 14:1
-
Tidskriftsartikel (refereegranskat)abstract
- The combination of the ability to absorb most of the solar radiation and simultaneously suppress infrared re-radiation allows selective solar absorbers (SSAs) to maximize solar energy to heat conversion, which is critical to several advanced applications. The intrinsic spectral selective materials are rare in nature and only a few demonstrated complete solar absorption. Typically, intrinsic materials exhibit high performances when integrated into complex multilayered solar absorber systems due to their limited spectral selectivity and solar absorption. In this study, we propose CoSbx (2 < x < 3) as a new exceptionally efficient SSA. Here we demonstrate that the low bandgap nature of CoSbx endows broadband solar absorption (0.96) over the solar spectral range and simultaneous low emissivity (0.18) in the mid-infrared region, resulting in a remarkable intrinsic spectral solar selectivity of 5.3. Under 1 sun illumination, the heat concentrates on the surface of the CoSbx thin film, and an impressive temperature of 101.7 °C is reached, demonstrating the highest value among reported intrinsic SSAs. Furthermore, the CoSbx was tested for solar water evaporation achieving an evaporation rate of 1.4 kg m−2 h−1. This study could expand the use of narrow bandgap semiconductors as efficient intrinsic SSAs with high surface temperatures in solar applications.
|
|
