Ab initio study of two-dimensional PdPS as an ideal light harvester and promising catalyst for hydrogen evolution reaction

The development of two-dimensional (2D) energy materials with high light absorption and ideal Gibbs free energy for hydrogen evolution reaction (HER) can propel us toward new technologies of efficient photoelectric conversion and clean energy production. Here our first-principles study depicts the 2D PdPS as a promising material for the photovoltaic solar cell and highly active catalyst for HER. Specifically, the calculated optical gap of PdPS monolayer is 1.65 eV, close to the ideal gap for solar cells. The PdPS monolayer shows a remarkably high absorbance in the visible light region and the exciton binding energy is estimated to be 0.55 eV. The PdPS sheet is found to possess highly active sites for HER, with the ideal value of Gibbs free energy, which is more desirable than that of Pt and MoS₂. Furthermore, we find the single-layer PdPS can be obtained experimentally by mechanical cleavage and it is dynamically stable by analysing its vibrational normal modes. Our work expands the family of 2D solar cells and the highly active HER activity of PdPS layer will place it as a promising catalyst for water splitting.