Engineering tantalum nitride for efficient photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting is a promising energy conversion strategy for directly converting solar energy into green hydrogen fuel. Constructing an efficient PEC device, finding an efficient photoanode material with a suitable band gap and favorable band-edge positions is essential. Tantalum nitride (Ta₃N₅) meets these fundamental requirements, and its theoretical maximum solar-to-hydrogen (STH) conversion efficiency can reach 15.9%. Consequently, it has been widely applied as a photoanode material for the PEC oxygen evolution reaction (OER). However, severe bulk and interface charge recombination, along with sluggish water oxygen kinetics, seriously limits its STH conversion efficiency for PEC water splitting. Herein, this feature article briefly reviews recent advances by our research group in improving the STH conversion efficiency of the Ta₃N₅ photoanode using various strategies, including defect engineering, construction of a gradient band structure, interface engineering, and surface modification of self-healing OER cocatalyst. Up to now, the obtained half-cell STH efficiency has exceeded 4%, providing a solid foundation for the development of tandem PEC devices for unbiased solar-driven overall water splitting toward practical application.