14.8% Quantum Efficient Gallium Phosphide Photocatalyst for Hydrogen Evolution

Abstract

Gallium phosphide is an established photoelectrode material for H 2 or O 2 evolution from water, but particle-based GaP photocatalysts for H 2 evolution are very rare. To understand the reasons, we investigated the photocatalytic H 2 evolution reaction (HER) of suspended n-type GaP particles with iodide, sulfite, ferricyanide, ferrous ion, and hydrosulfide as sacrificial electron donors, and using Pt, Rh y Cr 2−y O 3 , and Ni 2 P HER cocatalysts. A record apparent quantum efficiency of 14.8% at 525 nm was achieved after removing gallium and oxide charge trapping states from the GaP surface, adding a Ni 2 P cocatalyst to reduce the proton reduction overpotential, lowering the Schottky-barrier at the GaP−cocatalyst interface, adjusting the polarity of the depletion layer at the GaP−liquid interface, and optimizing the electrochemical potential of the electron donor. The work not only showcases the main factors that control charge separation in suspended photocatalysts, but it also explains why most known HER photocatalysts in the literature are based on n-type and not ptype semiconductors.

Fabrication of high-surface-area mesoporous frameworks of β-Ni(OH)2–CdIn2S4 p–n nano-heterojunctions for improved visible light photocatalytic hydrogen production

“…It should be stressed that elevating the β-Ni(OH) 2 Fermi level upon contact with CIS can effectively diminish the hole transfer barrier of the β-Ni(OH) 2 /liquid junction, facilitating a more efficient electron collection from the sacrificial donor in solution. 42 The redistribution of charge carriers at the p–n β-Ni(OH) 2 /CIS heterojunctions is in line with the observations from EIS and VB-XPS analyses. Indeed, all these effects undoubtedly contribute positively to the photocatalytic performance of the Ni/CIS NCFs catalysts.…”