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Graphical abstract Highlights • A thin IrO 2 film is uniformly coated on porous Ti mesh via anodic electrodeposition. • The IrO 2 film is an efficient catalyst layer for the oxygen evolution reaction. • A high current density (0.97 A cm−2 at 1.6 V) at 0.4 mg cm−2 is produced at 120 °C. • The electrodeposited film physically blocks exposure of the Ti diffusion layer. • The IrO 2 film protects against Ti corrosion and improves cell durability at 120 °C. Abstract In this study, IrO 2 -coated Ti mesh (e-IrO 2 /Ti) is proposed to be an efficient and durable oxygen electrode for high-temperature polymer-membrane-electrolyte water electrolyzers (HT-PEMWEs). A thin IrO 2 film of submicron thickness was uniformly coated onto a porous Ti mesh substrate by anodic electrodeposition. The electrodeposited IrO 2 film plays the dual role of a catalyst layer for the oxygen evolution reaction (OER), and a corrosion-protection layer that prevents oxidation of the inner Ti. The e-IrO 2 /Ti exhibited high performance (0.97 A cm−2 at 1.6 V) despite a low IrO 2 loading (0.4 mg cm−2) in single-cell tests conducted at 120 °C, which is comparable to that of conventional electrodes with greater catalyst loadings (0.8–5 mg cm−2). Furthermore, corrosion polarization tests reveal that the IrO 2 coating physically blocks exposure of the Ti diffusion layer, thereby reducing Ti corrosion by 82% in 0.5 M H 2 SO 4 at 25 °C. The low degradation rate (1.5 mA cm‐2 h−1 (0.11% h−1)) obtained in aging experiments at 120 °C and 1.72 V (voltage efficiency of 85%) confirms the excellent stability of this electrode. [ABSTRACT FROM AUTHOR]

Exploiting inexhaustible free energy from the sun to produce clean and sustainable fuels is an attractive route toward the heavily polluted earth and energy shortage. Photoelectrochemical cell is strategic energy device because the generated fuels can be stored and used on-demand. Herein, we present the fabrication of Si photoelectrodes with efficient charge separation and transfer using metal-insulator-semiconductor heterostructures for energy-rich fuel production via photoelectrochemical water and urea oxidation. With controls of the native SiO x insulator layer and catalytic NiFe metal layer, Si photoelectrode exhibits a photovoltage of 530 mV and a photocurrent density of 33.3 mA cm−2 at 1.23 V versus reversible hydrogen electrode. Further employed Ni(OH) 2 catalysts allow Si photoanode to achieve fill factor of 25.73% and solar-to-hydrogen conversion efficiency of 10.8% with a perovskite/Si tandem solar cell. The fabricated Ni(OH) 2 /NiFe/n-Si photoanode shows considerable performances toward urea oxidation. Our work presents new insights into sunlight-assisted hydrogen production using wastewater. [Display omitted] • Tailored MIS photoanode based on the insulating SiOx layer, composition-controlled NiFe metal film, and Ni(OH) 2 catalyst. • Spontaneous water oxidation with STH conversion efficiency of 10.8% implemented by the PV-PEC tandem device. • Urea oxidation with a low onset potential of 0.83 V vs. RHE by the nano-heterogeneous Ni(OH) 2 /Ni 0.5 Fe 0.5 /SiO x /n-Si photoanode. [ABSTRACT FROM AUTHOR]

To reduce the use of noble metals, iridium oxide (IrO 2 ) catalysts are prepared on carbon paper (CP) by electrodeposition for use as the anodes in polymer electrolyte membrane water electrolysis (PEMWE). The activities of the fabricated electrodes toward the oxygen evolution reaction are evaluated. The loading amount and morphology of the IrO 2 deposits are varied by controlling the electrodeposition potential ( E dep ) and time ( t dep ). When electrodeposited at 0.7 V, the IrO 2 loading ranges from 0.007 to 0.464 mg cm −2 ( t dep : 1 ∼ 30 min). In the PEMWE test at 90 °C, the IrO 2 /CP electrode with an IrO 2 loading of 0.1 mg cm −2 shows the highest performance (1.92 A cm −2 at 1.8 V) in which high IrO 2 utilization is achieved without significant exposure of the substrate carbon surface. The developed IrO 2 /CP electrodes provide cell performances comparable to those in previous reports with a higher IrO 2 loading, indicating markedly enhanced mass activity. [ABSTRACT FROM AUTHOR]