| 1. |
- Anil, Athira, et al.
(författare)
-
Effect of pore mesostructure on the electrooxidation of glycerol on Pt mesoporous catalysts
- 2023
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 11:31, s. 16570-16577
-
Tidskriftsartikel (refereegranskat)abstract
- Glycerol is a renewable chemical that has become widely available and inexpensive due to the increased production of biodiesel. Noble metal materials have shown to be effective catalysts for the production of hydrogen and value-added products through the electrooxidation of glycerol. In this work we develop three platinum systems with distinct pore mesostructures, e.g., hierarchical pores (HP), cubic pores (CP) and linear pores (LP); all with high electrochemically active surface area (ECSA). The ECSA-normalized GEOR catalytic activity of the systems follows HPC > LPC > CPC > commercial Pt/C. Regarding the oxidation products, we observe glyceric acid as the main three-carbon product (3C), with oxalic acids as the main two-carbon oxidation product. DFT-based theoretical calculations support the glyceraldehyde route going through tartronic acid towards oxalic acid and also help understanding why the dihydroxyacetone (DHA) route is active despite the absence of DHA amongst the observed oxidation products.
|
|
| 2. |
- Gao, Wenqiang, et al.
(författare)
-
Construction of diluted magnetic semiconductor to endow nonmagnetic semiconductor with spin-regulated photocatalytic performance
- 2023
-
Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 110
-
Tidskriftsartikel (refereegranskat)abstract
- Electron spinning polarization has now attracted extensive attention due to its significant effect on improving catalysis. However, only a few photocatalysts possess the electron spinning modification property. How to endow nonmagnetic semiconductors with spintronic properties to realize spinning-regulated photocatalysis enhancement is a great challenge. Herein, based on the diluted magnetic semiconductor concept, we proposed a novel strategy to endow photocatalysts a spinning tunable property. In this work, a diluted magnetic semiconductor photocatalyst with spin polarization was constructed by only doping magnetic ions into CdS/MoS2. The spin polarization with a higher ferromagnetic property was detected in CdS and MoS2 of the Ni-doped CdS/MoS2 diluted magnetic semiconductor photocatalyst. The magnetic field-derived spin polarization reduced the charge recombination in CdS, and improved the interface transfer efficiency between CdS and MoS2, which resulted in a 3.89-fold improvement of the photocatalytic hydrogen production under an external magnetic field. This work provides a new strategy to endow nonmagnetic semiconductors with spin-regulated photocatalytic performance by constructing diluted magnetic semiconductor photocatalysts.
|
|
| 3. |
- Hudson, Lawrence N, et al.
(författare)
-
The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project
- 2017
-
Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 7:1, s. 145-188
-
Tidskriftsartikel (refereegranskat)abstract
- The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.
|
|
| 4. |
- Lind, Elvira, et al.
(författare)
-
Catalyst layer utilisation during glycerol electrooxidation in alkaline media with electrodeposited Pd catalysts at different thicknesses
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The glycerol electrooxidation reaction (GEOR) has been increasingly studied for providing value-added chemical products whilst also facilitating a concurrent reduction process such as hydrogen evolution. Noble metals have been shown to be highly active for the GEOR in alkaline media. Here, to assess the effects of mass transport, catalyst layer thickness and pH on the GEOR, three thicknesses of Pd are electrodeposited onto a Ni rotating disk electrode and studied for a constant glycerol concentration of 0.50 M with NaOH to glycerol ratios of 1:2, 1:1 and 2:1. The electrodeposited catalysts are found to be morphologically similar with similar crystallographic structures. The activity, evaluated from the peak current density at the point of deactivation, shows that for every pH, the thinnest catalyst has the highest specific activity, whereas the thickest catalyst has the lowest. Therefore, there is a significant underutilisation of the thicker porous Pd electrodes for the GEOR. The thinnest catalyst layer is furthermore investigated in a solution of 1.0 M NaOH and 1.0 M glycerol. The doubling of the glycerol concentration in this case did not provide a significant increase in current density. Therefore, we propose that there is an optimal ratio of OHˉ to glycerol ratio in solution of around 2:1 due to the stoichiometry of the GEOR with the diffusion layer thickness and flux at higher glycerol concentrations considered.
|
|
| 5. |
- Martín-Yerga, Daniel, et al.
(författare)
-
Structure–Reactivity Effects of Biomass-based Hydroxyacids for Sustainable Electrochemical Hydrogen Production
- 2021
-
Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 14:8, s. 1902-1912
-
Tidskriftsartikel (refereegranskat)abstract
- Biomass electro-oxidation is a promising approach for the sustainable generation of H2 by electrolysis with simultaneous synthesis of value-added chemicals. In this work, the electro-oxidation of two structurally different organic hydroxyacids, lactic acid and gluconic acid, was studied comparatively to understand how the chemical structure of the hydroxyacid affects the electrochemical reactivity under various conditions. It was concluded that hydroxyacids such as gluconic acid, with a considerable density of C−OH groups, are highly reactive and promising for the sustainable generation of H2 by electrolysis at low potentials and high conversion rates (less than −0.15 V vs. Hg/HgO at 400 mA cm−2) but with low selectivity to specific final products. In contrast, the lower reactivity of lactic acid did not enable H2 generation at very high conversion rates (<100 mA cm−2), but the reaction was significantly more selective (64 % to pyruvic acid). This work shows the potential of biomass-based organic hydroxyacids for sustainable generation of H2 and highlights the importance of the chemical structure on the reactivity and selectivity of the electro-oxidation reactions.
|
|
| 6. |
- Terekhina, Irina, et al.
(författare)
-
Electrocatalytic Oxidation of Glycerol to Value-Added Compounds on Pd Nanocrystals
- 2023
-
Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 6:13, s. 11211-11220
-
Tidskriftsartikel (refereegranskat)abstract
- Pd octahedral, rhombic dodecahedral, and cubic nanoparticles (PdOCTA, PdRD, and PdCUBE NPs) were synthesized, characterized, and studied as catalysts for the glycerol electrooxidation reaction (GEOR) in a strongly alkaline medium at 20 and 60 °C. The highest mass activity of 0.050 and 0.183 mA/μgPd was observed on PdOCTA at 20 and 60 °C, respectively, whereas PdCUBE exhibited the highest specific activity of 1.49 and 12.84 mA/cmPd2, respectively. The GEOR products were analyzed by high-performance liquid chromatography (HPLC), and their selectivity and overall glycerol conversion were evaluated at 0.86 V vs RHE. The selectivity toward the three-carbon chain (C3) GEOR products was similar for the different types of catalysts, with PdOCTA and PdCUBE NPs achieving more than 50% selectivity at 20 °C and more than 60% at 60 °C. Glycerate was the overall dominant product for all catalysts, with a selectivity of up to 42%. The glycerol conversion was found to be highest for PdOCTA─21% at 20 °C and 82% at 60 °C, while PdRD was the least active and showed less than 3% conversion at 20 °C and 35% at 60 °C. Based on the GEOR product distribution, a reaction mechanism was proposed.
|
|
| 7. |
- White, Jai, et al.
(författare)
-
Crystallographic facet and alkali metal cation dependent glycerol electrooxidation on polycrystalline Pd probed by SECCM
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Glycerol is considered an important platform chemical for value-added organic chemical synthesis. The electrooxidation of glycerol in aqueous media provides a facile synthesis method to generate chemicals important for pharmaceutical and medical industries. Therefore, critical knowledge regarding the most active catalysts for the glycerol electrooxidation reaction (GEOR) is necessary for such a process to be viable. The GEOR on noble metals is well studied but there are significant gaps in the literature regarding the activity of specific crystal facets, particularly in the case of Pd. Through SECCM electrochemical mapping correlated with EBSD mapping to identify grain orientations, a much larger picture of the GEOR on Pd catalysts can be formed. Here, the facet dependent activity for the GEOR on Pd, evaluated through cyclic voltammetry using SECCM with co-located EBSD, is reported for the first time in alkaline solutions of KOH, NaOH and LiOH at pH 13. NaOH is shown to result in the highest performance for the GEOR and for all three electrolytes, Pd (111) provides the highest activity, Pd (001) provides intermediate to high activity and that Pd (101) is the least active. The facet dependent activity for the GEOR is directly mirrored for Pd oxidation and the subsequent PdO reduction process. Suggesting these two processes are signifiers towards catalytic activity for the GEOR.
|
|
| 8. |
- White, Jai, et al.
(författare)
-
Electrodeposited PdNi on a Ni rotating disk electrode highly active for glycerol electrooxidation in alkaline conditions
- 2022
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 403
-
Tidskriftsartikel (refereegranskat)abstract
- The development of alcohol-based electrolysis to enable the concurrent production of hydrogen with low electricity consumption still faces major challenges in terms of the maximum anodic current density achievable. Whilst noble metals enable a low electrode potential to facilitate alcohol oxidation, the deactivation of the catalyst at higher potentials makes it difficult for the obtained anodic current density to compete with water electrolysis. In this work the effect of significant parameters such as mass transport, glycerol and OH- concentration and electrolyte temperature on the glycerol electrooxidation reaction (GEOR) in alkaline conditions on a bimetallic catalyst PdNi/Ni-RDE (Pd0.9Ni0.1) has been studied to discern experimental conditions which maximise achievable anodic current density before deactivation occurs. The ratio of NaOH:glycerol in the electrolyte highly affects the rate of the GEOR. A maximum current density of 793 mA cm(-2) at-0.125 V vs. Hg/HgO through steady state polarisation curves was achieved at a moderate and intermediate rotation rate of 500 RPM in a 2 M NaOH and 1 M glycerol (ratio of 2) electrolyte at 80 & DEG;C. Shown here is a method of catalyst reactivation for enabling the longterm use of the PdNi/Ni-RDE for electrolysis at optimal conditions for extended periods of time (3 h at 300 mA cm(-2) and 10 h at 100 mA cm(-2)). Through scanning electron microscopy (SEM), X-ray photon electron spectroscopy (XPS) and X-ray diffraction (XRD) it is shown that the electrodeposition of Pd and Ni forms an alloy and that after 10 h of electrolysis the catalyst has chemical and structural stability. This study provides details on parameters significant to the maximising of the GEOR current density and the minimising of the debilitating effect that deactivation has on noble metal based electrocatalysts for the GEOR.
|
|
| 9. |
- White, Jai, 1991-
(författare)
-
From Facets to Flow: The Electrooxidation of Glycerol on Pd-based catalysts
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Glycerol, a by-product of biodiesel refineries, has uses in industries such as cosmetics, food, and pharmaceuticals. However, its usage is small compared to the amount of glycerol produced from biodiesel production. Therefore, there is an opportunity to use glycerol, an important platform chemical, as a cheap feedstock for the synthesis of valuable chemicals. These chemicals can be formed in aqueous media through the glycerol electrooxidation reaction (GEOR) on the anode with hydrogen gas concurrently generated on the cathode. This thesis focuses on the GEOR in alkaline media on Pd and PdNi catalysts. The works compiled here evaluate the GEOR using electrochemical methods such as cyclic voltammetry, galvanostatic polarisation curves, chronoamperometry and chronopotentiometry. Pd and PdNi catalysts were fabricated through chemical synthesis, and electrodeposition onto Ni substrates. Singularly oriented Pd crystal facets were studied, showing those approximating Pd (111) as the most active. Similarly faceted bimetallic PdNi nanoparticles proved significantly more active than pure Pd. Effects of mass transport, studied for Pd/NiRDE and PdNi/NiRDE, indicated performance effects linked to diffusion and underutilisation of thicker catalyst layers. In aerated solutions, industrially relevant current densities were achieved on PdNi/Nifoam in concentrated electrolytes at elevated temperatures for extended periods. The analysis of glycerol oxidation products, formed during steady state measurements, was done using high performance liquid chromatography. The two major products were consistently shown to be glycerate and lactate. This work, covering many aspects of the GEOR, shows that Pd-based catalysts have potential for future industrial application.
|
|
| 10. |
- White, Jai, et al.
(författare)
-
Glycerol Electrooxidation at Industrially Relevant Current Densities Using Electrodeposited PdNi/Nifoam Catalysts in Aerated Alkaline Media
- 2023
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 170:8
-
Tidskriftsartikel (refereegranskat)abstract
- Through glycerol electrooxidation, we demonstrate the viability of using a PdNi catalyst electrodeposited on Ni foam to facilitate industrially relevant rates of hydrogen generation while concurrently providing valuable organic chemicals as glycerol oxidation products. This electrocatalyst, in a solution of 2 M NaOH and 1 M glycerol at 80 °C, enabled current densities above 2000 mA cm−2 (in a voltammetric sweep) to be obtained in atmospheres of both air and N2. Repeated potential cycling under an aerated atmosphere to these exceptional current densities indicated a high stability of the catalyst. Through steady state polarisation curves, 1000 mA cm−2 was reached below an anodic potential of 0.8 V vs RHE. Chronoamperometry showed glycerate and lactate being the major oxidation products, with increased selectivity for lactate at the expense of glycerate in aerated systems. Aerated atmospheres were demonstrated to consistently increase the apparent Faradaic efficiency to >100%, as determined by the concentration of oxidation products in solution. The excellent performance of PdNi/Ni in aerated solutions suggests that O2 removal from the electrolyte is not needed for an industrial glycerol electrooxidation process, and that combining electrochemical and chemical glycerol oxidation, in the presence of dissolved O2, presents an important process advantage.
|
|
