G-C₃N₄, studied as a metal-free photocatalyst, can lead to excellent results but the recombination of photogenerated charge carriers can substantially limit its performance.

NiFe layered double hydroxide (NiFe-LDH) is a cost-effective and active catalyst for the oxygen evolution reaction (OER), yet further promoting its OER performance is an ongoing challenge. Herein, we devised a facile strategy that can form two types of Co introduced NiFe-LDH catalysts, namely CoNiFe-LDH and Co@NiFe-LDH. Multiple techniques disclosed that a heterostructure is formed between Co(OH)₂ and NiFe-LDH for Co@NiFe-LDH, while electronic interactions between Co and NiFe atoms are observed for both samples. Notably, Co@NiFe-LDH exhibited markedly superior OER performance to the RuO₂ benchmark in alkaline medium, manifested by a low overpotential of 253 mV at 10 mA cm⁻², an extremely small Tafel slope of 44 mV dec⁻¹, and the outperformed stability for long-time operation. Further, when employed as an air-cathode catalyst for rechargeable Zn–air batteries (ZABs), the Co@NiFe-LDH modified battery surpassed the Pt/C + RuO₂ decorated one, evidenced by a larger power density, a bigger specific capacity, and a superior galvanostatic charge–discharge cycling stability for 90 h. Density functional theory (DFT) calculations revealed that the Fe site is the active center for the OER, and the formation of the heterostructure can increase the density of states of the active site near the Fermi level hence significantly enhancing the electrical conductivity, while also upshifting the d-band center of the Fe site to increase the adsorption capability of the *OOH intermediate, resulting in the energy barrier of the rate determining step being reduced eventually.

A monoclinic BiVO₄ film was grown on a transparent conducting substrate for photoelectrochemical oxidation of water. A photocurrent up to 2.3 mA cm⁻² under visible light (λ > 420 nm) was achieved after treating the sample simply by electrochemical reduction followed by NaBH₄. The high photocurrent is believed to be due to the improved carrier separation and transportation as a result of increased donor density.

Sn-doped hematite films were electrochemically deposited on a fluorine-doped tin oxide substrate for use as an anode for photoelectrochemical water oxidation. A high photocurrent of ∼2.8 mA cm⁻² at 1.24 V vs. RHE and a conversion efficiency of 0.24% are achieved.

Phosphorus-doped TiO ₂ nanotube arrays have been prepared via a phosphine annealing protocol and have been found to be efficient as a photoanode for visible-light-driven water oxidation.