Electrocatalytic Glycerol Oxidation with Concurrent Hydrogen Evolution Utilizing an Efficient MoOx /Pt Catalyst.

Glycerol electrolysis affords a green and energetically favorable route for the production of value-added chemicals at the anode and H2 production in parallel at the cathode. Here, a facile method for trapping Pt nanoparticles at oxygen vacancies of molybdenum oxide (MoOx ) nanosheets, yielding a high-performance MoOx /Pt composite electrocatalyst for both the glycerol oxidation reaction (GOR) and the hydrogen evolution reaction (HER) in alkaline electrolytes, is reported. Combined electrochemical experiments and theoretical calculations reveal the important role of MoOx nanosheets for the adsorption of glycerol molecules in GOR and the dissociation of water molecules in HER, as well as the strong electronic interaction with Pt. The MoOx /Pt composite thus significantly enhances the specific mass activity of Pt and the kinetics for both reactions. With MoOx /Pt electrodes serving as both cathode and anode, two-electrode glycerol electrolysis is achieved at a cell voltage of 0.70 V to reach a current density of 10 mA cm-2 , which is 0.90 V less than that required for water electrolysis.

Structure-Reactivity Effects of Biomass-based Hydroxyacids for Sustainable Electrochemical Hydrogen Production.

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.

Single atom tungsten doped ultrathin α-Ni(OH)2 for enhanced electrocatalytic water oxidation.

Electrocatalytic water oxidation is a rate-determining step in the water splitting reaction. Here, we report one single atom W6+ doped Ni(OH)2 nanosheet sample (w-Ni(OH)2) with an outstanding oxygen evolution reaction (OER) performance that is, in a 1 M KOH medium, an overpotential of 237 mV is obtained reaching a current density of 10 mA/cm2. Moreover, at high current density of 80 mA/cm2, the overpotential value is 267 mV. The corresponding Tafel slope is measured to be 33 mV/dec. The d0 W6+ atom with a low spin-state has more outermost vacant orbitals, resulting in more water and OH- groups being adsorbed on the exposed W sites of the Ni(OH)2 nanosheet. Density functional theory (DFT) calculations confirm that the O radical and O-O coupling are both generated at the same site of W6+. This work demonstrates that W6+ doping can promote the electrocatalytic water oxidation activity of Ni(OH)2 with the highest performance.