Graphene Mediates Charge Transfer between Lead Chromate and a Cobalt Cubane Cocatalyst for Photocatalytic Water Oxidation

Abstract

The interfacial barrier of charge transfer from semiconductors to cocatalysts means that the photogenerated charges cannot be fully utilized, especially for the challenging water oxidation reaction. Using cobalt cubane molecules (Co₄ O₄ ) as water oxidation cocatalysts, we rationally assembled partially oxidized graphene (pGO), acting as a charge-transfer mediator, on the hole-accumulating {-101} facets of lead chromate (PbCrO₄ ) crystal. The assembled pGO enables preferable immobilization of Co₄ O₄ molecules on the {-101} facets of the PbCrO₄ crystal, which is favorable for the photogenerated holes transferring from PbCrO₄ to Co₄ O₄ molecules. The surface charge-transfer efficiency of PbCrO₄ was boosted by selective assembly of pGO between PbCrO₄ and Co₄ O₄ molecules. An apparent quantum efficiency for photocatalytic water oxidation on the Co₄ O₄ /pGO/PbCrO₄ photocatalyst exceeded 10 % at 500 nm. This strategy of rationally assembling charge-transfer mediator provides a feasible method for acceleration of charge transfer and utilization in semiconductor photocatalysis.

Keywords: Charge-Transfer Mediator; Lead Chromate; Photocatalysis; Spatial Charge Separation; Water Oxidation Cocatalysts.