Quasi-2D PdSi2–xGexN4 (x = 0, 1, 2): Promising Candidates for Spontaneous Overall Water Splitting

Searching for ecofriendly and highly efficient photocatalysts for renewable energy conversion has been an ongoing challenge. Inspired by the successful synthesis of quasi-2D MoSi2N4 and WSi2N4, we investigated three members of this family, PdSi2N4, Janus PdSiGeN4, and PdGe2N4, indicating excellent stability and promising photocatalytic performance using ab initio calculations. All three systems possess appropriate semiconducting band gaps and band edge alignments with robust chemical/dynamical stability. All three systems show excellent hydrogen evolution and oxygen evolution reaction (HER and OER) overpotentials to self-sustain the photocatalytic mechanism. PdGe2N4 turns out to be the best candidate for HER activity, with Gibbs free energy (ΔG) as low as −0.03 eV, even better than that of the traditional Pt catalyst (−0.09 eV). In the case of OER, ΔG is negative for all three systems (under the influence of the potential supplied by photogenerated holes), indicating that the process is spontaneous and no overpotential is required. We strongly believe that the promising photocatalytic performance of these quasi-2D systems reported here will open doors for their future experimental studies.