(Invited) 14.8% Quantum Efficient Gallium Phosphide Photocatalyst for Hydrogen Evolution

Gallium phosphide is a well-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 AQE of 14.8% at 525 nm was achieved after removing charge trapping states from the GaP surface, adding a Ni 2 P cocatalyst to reduce the proton reduction overpotential, lowering the Schottky-barriers at the GaP-cocatalyst and GaP-liquid interfaces, and adjusting the electrochemical potential of the electron donor. The work showcases the main factors that control charge separation in suspended photocatalysts, and it explains why most known HER photocatalysts in the literature are based on n-type and not p-type semiconductors.