Hydrogen production by water reduction on Si photocathode coupled with Ni2P.

Abstract While searching for an efficient, non-noble, earth-abundant catalyst for the hydrogen evolution reaction (HER), we synthesized hexagonal dinickel phosphide with different nanostructures using solvothermal phosphidation. Coupled atop p- type Si, this catalyst performed as a p-n heterojunction photocathode assembly and the performance varied when under different electrolyte media. Apart from changing the surface morphology, Ni 2 P was crystallized with an increase in the Niδ+/Ni2+ ratio as the phosphidation temperature gradually increased. A systematic evaluation of the water splitting reaction shows that a very small amount of catalyst (>85% transmittance for the catalyst layer) exhibits a photocurrent of −10 mA cm−2 with a positive applied potential of 0.05 V versus reversible hydrogen electrode under simulated solar irradiation of AM 1.5G. We discuss the substantial charge transfer process at the depletion layer of the electrode/catalyst and the catalyst/electrolyte interface. Mott–Shottky analysis showed a shift in the flat band potential for Ni 2 P, which reveals the underlying mechanism for the role of the p-n junction for enhanced photoelectrochemical cell performance. Highlights • The Hexagonal phase Ni 2 P is changing Niδ+/Ni2+ ratio with phosphidation temperature. • p- Si coupled with as-prepared Ni 2 P performed as p-n heterojunction photocathode unit. • Optimized photocurrent obtained with 10 mA cm−2 at positive applied potential of 0.05 V. • Shifting of flat-band potential validated the charge transfer process. [ABSTRACT FROM AUTHOR]