Electronic and Photocatalytic Properties of Ag3PC4VI (C = O, S, Se): A Systemic Hybrid DFT Study

Recently developed photoelectrode Ag3PO4 exhibits extremely high quantum yield (up to 90% at 420 nm) of O2 generation from water oxidation, but it can only absorb part of visible light and cannot reduce water to release H2. It is still a challenge to develop the high performance water splitting photocatalysts toward broader solar spectrum response. We theoretically investigated the electronic and photocatalytic properties of Ag3PC4VI (C = O, S, Se) by the hybrid density functional method. The experimental band gap of Ag3PO4 (2.45 eV) was well reproduced by this level of theory (2.49 eV). We found that orthorhombic Ag3PSe4 presents not only an ideal direct band gap (2.09 eV) to harvest a large part of solar light in the visible range but also suitable reduction potential (−0.275 V vs normal hydrogen electrode, NHE) for water reduction. Ag3PS4 has a relatively larger band gap of 2.88 eV, but it has a rather negative reduction potential (−0.53 V vs NHE). The analysis of the density of states and the single-state charge densities suggested that the weakened P–CVI bonds and the disappearance of Ag–Ag interaction from Ag3PO4 to Ag3PC4VI(C = S, Se) result in the great change of the conduction band minimum from the highly delocalized Ag s orbitals to the strong mixing of P–Se(S) orbitals. The potential problems of stability and photocorrosion for Ag3PC4VI(C = S, Se) were also discussed. Our theoretical results demonstrated that Ag3PC4VI(C = S, Se) both are potential candidates for the photocatalytic hydrogen generation from water.