Toward efficient photocatalytic pure water splitting for simultaneous H2 and H2O2 production

Abstract

Although overall water splitting with particulate photocatalysts is considered as an ideal means towards solar-to-hydrogen conversion, practical application of the promising technique is greatly inhibited by the congenital defects including H2/O2 separation and unfavorable four-electron kinetics. In this context, photocatalytic overall water splitting for simultaneous H2 and H2O2 generation via a two-electron pathway can readily address these issues. Here, we report a novel CoxNiyP cluster incorporated P-doped g-C3N4 photocatalyst (CoxNiyP-PCN) by a two-step phosphating method that presents such unique behavior for pure water splitting into stoichiometric H2 and H2O2. The highest H2 evolution rate reaches 239.3 μmol h−1 g−1, achieved over the CoNiP–PCN photocatalyst, which is among the best reported activities for overall water splitting. It is found that both P and the cluster cocatalyst are critical to the remarkably improved photocatalytic activity. Specifically, P as a substitution of C in PCN introduces a positive charge center (P+), reinforcing the chemical connection between PCN and CoNiP, in a form of P+-Pδ--Coδ+/Niδ+. This unique bridging effect, together with the extended light absorption by P doping and optimized surface redox potential by cocatalyst integration, stimulates efficient vectorial charge transfer between PCN and CoNiP and subsequent surface mass exchange. On the other hand, we also demonstrate that the well satisfied band structure of PCN can facilitate the two-electron reaction pathway. This work not only has implications for the potential use of CoNiP–PCN as potential photocatalyst for solar H2 production, but also offers a new idea for pure water slitting in particulate system.