Ag2CdP2S6 2D semiconductor photocatalyst: Pioneering efficient green hydrogen production through solar water splitting

Abstract

The escalating global pollution crisis, largely driven by fossil fuel consumption in industrial sectors responsible for approximately 75% of global greenhouse gas emissions, underscores the urgent need for sustainable clean energy solutions to achieve decarbonization targets. This study explores the potential of Ag₂CdP₂S₆, a novel two-dimensional (2D) semiconductor, as an effective photocatalyst for green hydrogen production through solar water splitting. Using density functional theory (DFT) calculations, we confirm the material’s dynamic and thermal stability via phonon analysis and ab initio molecular dynamics (AIMD) simulations. Band structure analyses reveal a semiconducting nature with a direct band gap of approximately $1.95\mathrm{eV}$ and $3.15\mathrm{eV}$ at DFT-PBE and DFT-HSE06 levels, respectively. Notably, absorption coefficient analysis demonstrates significant peaks in the ultraviolet region $(149620{\mathrm{cm}}^{-1},8.57\mathrm{eV})$ alongside considerable visible light absorption $(11564{\mathrm{cm}}^{-1},3.26\mathrm{eV})$. The conduction band minimum (CBM) is calculated at $-3.69\mathrm{eV}$, and the valence band maximum (VBM) at $-6.84\mathrm{eV}$, satisfying the criteria for effective hydrogen evolution reaction (HER). Under acidic conditions, optimal HER kinetics are observed at phosphorus (P) atom sites with a near-ideal Gibbs free energy change ($\Delta G_H^{\ast }$) of approximately $-0.02\mathrm{eV}$. Meanwhile, tilted sulfur (S) sites exhibit superior water splitting efficiency at neutral ($pH=7$) and slightly alkaline conditions ($pH=8.3$), with $\Delta G_H^{\ast }$ values of $0.66\mathrm{eV}$ and $0.51\mathrm{eV}$, respectively. These findings highlight the versatility and efficiency of Ag₂CdP₂S₆ as photocatalyst across diverse pH conditions, characterized by enhanced charge transfer properties, thereby contributing to the advancement of renewable hydrogen production technologies.