Two-Dimensional AlN/PtSSe Heterojunction as A Direct Z-Scheme Photocatalyst for Overall Water Splitting: A DFT Study

Abstract

The conversion of solar energy into hydrogen energy using photocatalysis technology is of great significance for the green and sustainable development of global energy. However, the lower catalytic efficiency limits the practical application of hydrogen production by the photolysis of water. In this work, a two-dimensional AlN/SPtSe-I van der Waals heterojunction is cleverly designed, and its photocatalytic water-splitting performance is investigated by first-principles calculations. Our results suggest that AlN/SPtSe-I shows narrower band gaps, suitable band edge positions, stronger light absorption, and separated photogenerated electron−hole pairs, showing excellent photocatalytic performance. Furthermore, based on the catalytic reaction mechanism of type-II and direct Z-scheme heterojunction, we calculated the Gibbs free energy of different intermediates in the entire process of photocatalytic water splitting and determined from the perspective of the reaction kinetics that AlN/SPtSe-I belongs to a typical direct Z-scheme heterojunction, indicating that it has a stronger redox ability. Interestingly, the AlN/SPtSe-I heterostructure can realize the spontaneous photolysis of water under neutral conditions, which significantly improves the photocatalytic efficiency. This work not only demonstrates that AlN/SPtSe-I is a potentially efficient photocatalytic water-splitting catalyst but also elucidates the methods for determining type-II and direct Z-scheme heterojunctions, providing theoretical guidance for designing efficient and highly stable photocatalysts.