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 (Co 3 (PO 4 ) 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 (Co 3 (PO 4 ) 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 Co 3 (PO 4 ) 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 Co 3 (PO 4 ) 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 Co 3 (PO 4 ) 2 nanospheres as a low-cost and more abundant electrocatalyst for direct methanol fuel cells.

Photoelectrochemical water splitting with metal oxide semiconductors offers a cost-competitive alternative for the generation of solar fuels. Most of the materials studied so far suffer from poor charge-transfer kinetics at the semiconductor/liquid interface, making compulsory the use of catalytic layers to overcome the large overpotentials required for the water oxidation reaction. Herein, we report a very soft electrolytic synthesis deposition method, which allows remarkably enhanced water oxidation kinetics of BiVO photoanodes by the sequential addition of Zr and Fe precursors. Upon a heat treatment cycle, these precursors are converted into monoclinic ZrO and α-Fe O nanoparticles, which mainly act as catalysts, leading to a five-fold increase of the water oxidation photocurrent of BiVO . This method provides a versatile platform that is easy to apply to different semiconductor materials, fully reproducible, and facile to scale-up on large area conductive substrates with attractive implications for technological deployment.

Photoelectrochemical water splitting using semiconductor materials has emerged as a promising approach to produce hydrogen (H 2 ) from renewable resources such as sunlight and water. In the present study, Ag 3 PO 4 nanoparticles were electrodeposited on BiVO 4 photoanodes for water splitting. A remarkable water oxidation photocurrent of 2.3 mA•cm −2 at 1.23 V versus reversible hydrogen electrode with ∼100% Faradaic efficiency was obtained, which constitutes a notable increase compared to the pristine BiVO 4 photoanode. It is demonstrated that the enhancement of optical absorption (above-band gap absorbance) and the decrease of surface losses after the optimized deposition of Ag/Ag 3 PO 4 nanoparticles are responsible for this notable performance. Remarkably, this heterostructure shows promising stability, demonstrating 25% decrease of photocurrent after 24 h continuous operation. This approach may open new avenues for technologically exploitable water oxidation photoanodes based on metal oxides. 50 metal oxides as candidate materials for the production of solar 51 fuels. 4−8 52 On the other hand, the best water oxidation catalysts 53 reported to date are based on scarce and expensive materials 54 such as IrO 2 or RuO 2 , which also suffer from low stability under 55 harsh environments, precluding large technological deploy-56 ment. Consequently, during the last years, an extensive research 57 activity targeting upscalable water oxidation catalysts has been 58 developed. One of the most promising materials reported to 59 date is silver phosphate, Ag 3 PO 4 , a semiconductor material with 60 an indirect band gap of 2.45 eV, able to absorb light up to 500 61 nm in the visible region. 9,10 Its valence band minimum is 62 located at 2.67 V versus reversible hydrogen electrode (RHE), 63 more positive than the thermodynamic potential for water 64 oxidation (1.23 V vs RHE). 9 Consequently, Ag 3 PO 4 has the 65 ability to oxidize H 2 O to produce O 2 , which makes this material 66 an attractive candidate for photocatalytic water oxidation. The 67 potential of Ag 3 PO 4 as a functional material for photo-68 electrocatalytic applications was first reported by Yi et al., 11 69 showing an extremely high performance for water oxidation 70 under visible light irradiation. In particular, they reported 90% 71 quantum efficiency for O 2 evolution with this material.

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