Hydrogen-substituted graphdiyne encapsulated cuprous oxide photocathode for efficient and stable photoelectrochemical water reduction

Abstract

Photoelectrochemical (PEC) water splitting is an appealing approach for "green" hydrogen generation. The natural p-type semiconductor of Cu₂O is one of the most promising photocathode candidates for direct hydrogen generation. However, the Cu₂O-based photocathodes still suffer severe self-photo-corrosion and fast surface electron-hole recombination issues. Herein, we propose a facile in-situ encapsulation strategy to protect Cu₂O with hydrogen-substituted graphdiyne (HsGDY) and promote water reduction performance. The HsGDY encapsulated Cu₂O nanowires (HsGDY@Cu₂O NWs) photocathode demonstrates a high photocurrent density of -12.88 mA cm^-2 at 0 V versus the reversible hydrogen electrode under 1 sun illumination, approaching to the theoretical value of Cu₂O. The HsGDY@Cu₂O NWs photocathode as well as presents excellent stability and contributes an impressive hydrogen generation rate of 218.2 ± 11.3 μmol h^-1cm^-2, which value has been further magnified to 861.1 ± 24.8 μmol h^-1cm^-2 under illumination of concentrated solar light. The in-situ encapsulation strategy opens an avenue for rational design photocathodes for efficient and stable PEC water reduction.