TiO₂/TiN Interface Enables Integration of Ni₅P₄ Electrocatalyst with a III–V Tandem Photoabsorber for Stable Unassisted Solar-Driven Water Splitting

Abstract

H 2 production by direct photoelectrochemical (PEC) water splitting has remained unachievable commercially, mainly due to rapid failure at the interface between the photoabsorber(s) and catalyst(s). PEC devices made from multijunction III−V semiconductors with platinum group metal (PGM) catalysts have yielded impressive initial solar-to-H 2 (STH) efficiency >19%, which rapidly corrodes in aqueous electrolytes. Here, TiO 2 /TiN layers were fused to create a bifunctional interface between a GaInP 2 /GaAs III−V tandem photoabsorber and a polycrystalline Ni 5 P 4 HER catalyst. The TiO 2 serves as a conducting corrosion barrier, while a thin layer of much denser TiN (1 nm) blocks interlayer diffusion during fabrication. This strategy allows the elevated temperatures needed to crystallize the Ni 5 P 4 nanoparticles and fuse to the TiO 2 / TiN junction to achieve minimal optical loss without damaging the sensitive photoasbsorber. The resulting photocathode exhibits an initial STH efficiency of 11.4%−13.2% in sodium phosphate electrolyte at neutral pH 7. It operated continuously for over 200 h without failure above 10% STH efficiency, exceeding all previous benchmarks. The earth-abundant Ni 5 P 4 catalyst replaces costly PGM catalysts at comparable HER activity in neutral, acidic, or basic pH electrolytes.

Recent Developments in Nickel-Based Layered Double Hydroxides for Photo(-/)electrocatalytic Water Oxidation

“…For example, Mi et al recently achieved a record-setting STH efficiency of up to 9.2% using an indium gallium nitride photocatalyst under concentrated simulated solar light . Hwang et al utilized the GaInP 2 /GaAs/TiO 2 /TiN/Ni 5 P 4 photoelectrode to realize STH efficiency of 11.4%–13.2% in sodium phosphate electrolyte at neutral pH = 7 . Overall, the design and development of catalytic materials are crucial for the three water decomposition technologies.…”

Shaping the Future of the Neurotransmitter Sensor: Tailored CdS Nanostructures for State-of-the-Art Self-Powered Photoelectrochemical Devices

“…The cutting-edge photoelectrochemical (PEC) analysis technology stands out with its extraordinary sensitivity and selectivity, operating on the fundamental principle of transforming light energy into electrical energy to enable precise examination of chemical substances in samples through electrochemical reactions. − With its vast potential for revolutionizing portable noninvasive DA monitoring systems, PEC analysis technology encounters challenges due to specific factors like limited photon absorption, restricted carrier directional transfer, and sluggish redox rates at interfaces. − Henceforth, it becomes crucial to engineer highly efficient photoelectronic semiconductor nanomaterials capable of maximizing photon utilization while enhancing photoelectric conversion efficiency …”