Two-Dimensional Arsenene/ZrS2(HfS2) Heterostructures as Direct Z-Scheme Photocatalysts for Overall Water Splitting

Searching for high-efficiency photocatalysts for overall water splitting is a promising strategy to solve the energy crisis and environmental problems. Among many kinds of photocatalysts, direct Z-scheme systems have attracted much attention. Here, we propose two-dimensional arsenene/ZrS2(HfS2) heterostructures as potential direct Z-scheme photocatalysts based on density functional theory simulations. Our calculations demonstrate that arsenene/ZrS2(HfS2) heterostructures have type-II band alignments with small band gaps, facilitating spatial separation of photo-generated carriers and enhancing sunlight absorption ability. Meanwhile, interlayer charge transfer induces a built-in electric field, resulting in the band edge positions bending at the interface region. Combined with the closed band edge positions and small interlayer band gaps, the direct Z-scheme charge transfer pathway is confirmed for them. Additionally, both heterostructures show energic, dynamical, and thermal stability based on the calculated results. What is more, under solar irradiation, the hydrogen evolution reaction and oxygen evolution reaction can be triggered spontaneously on different monolayers with the potential supplied by photo-generated electrons and holes based on the calculated free energy difference (ΔG). Therefore, arsenene/ZrS2(HfS2) heterostructures may have promising potential as bifunctional photocatalysts for overall water splitting. This work provides valuable guidance for designing the direct Z-scheme photocatalysts.