Low-cost and high-performance advanced electrocatalysts for direct methanol fuel cells are of key significance for the improvement of environmentally-pleasant energy technologies. Herein, we report the facile synthesis of cobalt phosphate (Co₃(PO₄)₂) nanospheres by a microwave-assisted process and utilized as an electrocatalyst for methanol oxidation. The phase formation, morphological surface structure, elemental composition, and textural properties of the synthesized (Co₃(PO₄)₂) nanospheres have been examined by powder X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), field emission-scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption-desorption isotherm investigations. The performance of an electrocatalytic oxidation of methanol over a Co₃(PO₄)₂ nanosphere-modified electrode was evaluated in an alkaline solution using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. Detailed studies were made for the methanol oxidation by varying the experimental parameters, such as catalyst loading, methanol concentration, and long-term stability for the electro-oxidation of methanol. The good electrocatalytic performances of Co₃(PO₄)₂ should be related to its good surface morphological structure and high number of active surface sites. The present investigation illustrates the promising application of Co₃(PO₄)₂ nanospheres as a low-cost and more abundant electrocatalyst for direct methanol fuel cells.

Electrooxidation of urea plays a substantial role in the elimination of urea-containing wastewater and industrial urea. Here, we report the electrodeposition of nickel hydroxide catalyst on commercial carbon paper (CP) electrodes from dimethyl sulphoxide solvent (Ni(OH)₂-DMSO/CP) for urea electrooxidation under alkaline conditions. The physicochemical features of Ni(OH)₂-DMSO/CP catalysts using scanning electron microscopy and X-ray photoelectron spectroscopy revealed that the Ni(OH)₂-DMSO/CP catalyst shows nanoparticle features, with loading of <1 wt%. The cyclic voltammetry and electrochemical impedance spectroscopy revealed that the Ni(OH)₂-DMSO/CP electrode has a urea oxidation onset potential of 0.33 V vs. Ag/AgCl and superior electrocatalytic performance, which is a more than 2-fold higher activity in comparison with the counterpart Ni(OH)₂ catalyst prepared from the aqueous electrolyte. As expected, the enhancement in electrocatalytic activity towards urea was associated with the superficial enrichment in the electrochemically active surface area of the Ni(OH)₂-DMSO/CP electrodes. The results might be a promising way to activate commercial carbon paper with efficient transition metal electrocatalysts, for urea electrooxidation uses in sustainable energy systems, and for relieving water contamination.

N-BiVO₄ is a favorable photoelectrode candidate for a photoelectrochemical (PEC) water splitting reaction owing to its suitable energy level edge locations for an oxygen evolution reaction. On the other hand, the sluggish water oxidation kinetics of BiVO₄ photoanodes when used individually make it necessary to use a hole blocking layer as well as water oxidation catalysts to overcome the high kinetic barrier for the PEC water oxidation reaction. Here, we describe a very simple synthetic strategy to fabricate nanocomposite photoanodes that synergistically address both of these critical limitations. In particular, we examine the effect of a SnO₂ buffer layer over BiVO₄ films and further modify the photoanode surface with a crystalline nickel tungstate (NiWO₄) nanoparticle film to boost PEC water oxidation. When NiWO₄ is incorporated over BiVO₄/SnO₂ films, the PEC performance of the resultant triple-layer NiWO₄/BiVO₄/SnO₂ films for the oxygen evolution reaction (OER) is further improved. The enhanced performance for the PEC OER is credited to the synergetic effect of the individual layers and the introduction of a SnO₂ buffer layer over the BiVO₄ film. The optimized NiWO₄/BiVO₄/SnO₂ electrode demonstrated both enriched visible light absorption and achieves charge separation and transfer efficiencies of 23% and 30%, respectively. The photoanodic current density for the OER on optimized NiWO₄/BiVO₄/SnO₂ photoanode shows a maximum photocurrent of 0.93 mA/cm² at 1.23 V vs. RHE in a phosphate buffer solution (pH~7.5) under an AM1.5G solar simulator, which is an incredible five-fold and two-fold enhancement compared to its parent BiVO₄ photoanode and BiVO₄/SnO₂ photoanodes, respectively. Further, the incorporation of the NiWO₄ co-catalyst over the BiVO₄/SnO₂ film increases the interfacial electron transfer rate across the composite/solution interface.

Photoanodes fabricated by the electrophoretic deposition of a thermally prepared zinc tantalum oxynitride (ZnTaO₂N) catalyst onto indium tin oxide (ITO) substrates show photoactivation for the oxygen evolution reaction (OER) in alkaline solutions. The photoactivity of the OER is further boosted by the photodeposition of cobalt phosphate (CoPi) layers onto the surface of the ZnTaO₂N photoanodes. Structural, morphological, and photoelectrochemical (PEC) properties of the modified ZnTaO₂N photoanodes are studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet visible (UV−Vis) diffuse reflectance spectroscopy, and electrochemical techniques. The presence of the CoPi layer significantly improved the PEC performance of water oxidation in an alkaline sulphate solution. The photocurrent-voltage behavior of the CoPi-modified ZnTaO₂N anodes was improved, with the influence being more prominent at lower oxidation potentials. A stable photocurrent density of about 2.3 mA·cm⁻² at 1.23 V vs. RHE was attained upon visible light illumination. Relative to the ZnTaO₂N photoanodes, an almost three-fold photocurrent increase was achieved at the CoPi/ZnTaO₂N photoelectrode. Perovskite-based oxynitrides are modified using an oxygen-evolution co-catalyst of CoPi, and provide a new dimension for enhancing the photoactivity of oxygen evolution in solar-assisted water-splitting reactions.