Van der Waals Heterostructures Comprised of Ultrathin Polymer Nanosheets for Efficient Z-Scheme Overall Water Splitting

Abstract

Inspired by natural photosynthesis, Z-scheme photocatalytic systems are very appealing for achieving efficient overall water splitting. Developing metal-free Z-scheme photocatalysts for overall water splitting, however, still remains challenging. The construction of polymer-based van der Waals heterostructures as metal-free Z-scheme photocatalytic systems for overall water splitting is described using aza-fused microporous polymers (CMP) and C₂ N ultrathin nanosheets as O₂ - and H₂ -evolving catalysts, respectively. Although neither polymer is able to split pure water using visible light, a 2:1 stoichiometric ratio of H₂ and O₂ was observed when aza-CMP/C₂ N heterostructures were used. A solar-to-hydrogen conversion efficiency of 0.23 % was determined, which could be further enhanced to 0.40 % by using graphene as the solid electron mediator to promote the interfacial charge-transfer process. This study highlights the potential of polymer photocatalysts for overall water splitting.

Keywords: Z-scheme; photocatalysis; polymer nanosheets; van der Waals heterostructures; water splitting.