Constructing a tandem heterojunction: S-scheme heterojunction and Ohmic junction based on graphdiyne, synergistically optimizing photocatalytic hydrogen evolution

Abstract

The construction of heterojunctions is often considered an effective strategy for achieving solar driven photocatalytic decomposition of water. Graphdiyne has unique properties such as highly π conjugated structure, ideal direct bandgap, and high charge carrier mobility, making it a candidate for ideal photocatalysts. In this work, a graphdiyne based composite catalyst GDY-Cu with ohmic contact interface was prepared through organic synthesis. Subsequently, a S-scheme heterojunction was constructed between the contact interface of WO3 nanorods with surface defects and GDY-Cu samples to promote electron transfer. The hydrogen evolution ability of GDY-Cu/WO3 samples with different ratios was studied by adjusting the addition amount of GDY-Cu. In addition, GDY-Cu/WO3 samples exhibits the highest photocatalytic hydrogen evolution activity, reaching 12.2 times that of pure GDY. In fact, the joint construction of Ohmic junctions and S-scheme heterojunctions provides a unique transport pathway for electron transfer. The built-in electric field between interfaces provides power for electron migration. Importantly, in-depth research on in-situ XPS and density functional theory calculations has confirmed the charge transfer pathway. Thorough charge dynamics analysis of the migration ability of photo generated charge carriers. This work not only enriches the photocatalytic system by integrating Ohmic junctions and S-scheme heterojunctions, but also provides a new design strategy for constructing graphdiyne based materials.