Dual-atom catalysts versus single-atom catalysts for bifunctional pH-universal water splitting

Developing efficient and stable bifunctional electrocatalysts for water splitting across a wide pH range remains a critical challenge in sustainable hydrogen production. We report a density functional theory investigation of single-atom catalysts (SACs) and dual-atom catalysts (DACs) supported on transition-metal chalcogenide monolayers (NiX, X = S, Se, Te) for overall water splitting over a broad pH range. DACs exhibit significantly enhanced hydrogen and oxygen evolution activity owing to dual-metal synergy, optimized intermediate adsorption, and efficient charge transfer. Among these, RhRh-A/NiTe demonstrates the lowest overpotentials and exceptional stability under acidic, neutral, and alkaline conditions, validated by molecular dynamics simulations. Electronic structure analyses, including d-band center positions, charge density differences, and density of states, attribute the improved catalytic activity to tuned adsorption energetics and enhanced electron delocalization. Our work provides insights into multi-atomic active sites and presents a rational approach for developing efficient, stable, and scalable electrocatalysts applicable across universal pH conditions.