Interface-engineered silicon photocathodes with a NiCoP catalyst-modified TiO2 nanorod array outlayer for photoelectrochemical hydrogen production in alkaline solution

To assemble efficient photoelectrochemical (PEC) cells for total water splitting, the inexpensive photocathodes that are active and stable in alkaline solutions are strongly desired, as the known earth abundant catalystdecorated photoanodes display high activity and good stability for water oxidation mostly in basic media. Herein, we report a Si-based composite photocathode with its front surface coated orderly by an N-doped graphene nanolayer (C-N) and a TiO2 nanorod array (TiO2(ALD/NR)), which is loaded with Ni/Co phosphide catalyst (NiCoP) nanoparticles. The optimized Si/C-N/TiO2(ALD/NR)/NiCoP electrode exhibits a photocurrent density of -19.87 mA cm(-2 )at 0 V, an onset potential at 0.42 V vs RHE, and an applied bias photon-to-current efficiency of 1.28% for H-2 production in 1.0 M KOH under simulated 1 sun illumination. The impacts of TiO2NR array outlayer and surface-loaded NiCoP catalyst on interfacial energetics, charge transfer kinetics, and PEC performance of photocathodes are comparatively studied by using a series of reference electrodes. The results indicate that the TiO2NR array makes a major contribution to the evidently improved PEC activity of Si/Co/TiO2(ALD/NR), and that the NiCoP loaded on the surface of TiO2 NR array greatly enhances the charge transfer efficiency and boosts HER kinetics of the photocathode.

Automated summary

The study focuses on the performance of a Si-based composite photocathode and its application in water splitting. The photocathode is modified with N-doped graphene and TiO2 nanorods, and loaded with Ni/Co phosphide catalyst to enhance its photoelectrochemical properties. The results show that the TiO2 nanorod array significantly improves the PEC activity, while the surface-loaded NiCoP catalyst enhances charge transfer efficiency and boosts HER kinetics.