Single-Atom Electrocatalysts Anchored on Phosphoniobic Acid (M₁/PNb₁₂O₄₀) Cluster for Water Splitting (HER/OER) and Metal-Air Batteries (ORR)

Single-atom catalysts (SACs) have revolutionized industrial catalysis due to their single active site, efficient use of active atoms, superior catalytic efficiency, and selectivity. Using first-principles calculations, we investigate the electrocatalytic performance of transition metal (Sc-Au) SACs anchored on phosphoniobic acid (PNbA) for hydrogen-evolution reaction (HER), and oxygen evolution/reduction reaction (OER/ORR). The 4-fold hollow site of PNbA facilitates electron transfers during catalysis. Through the Heyrovsky pathway, the Ru₁/PNbA, Rh₁/PNbA, Ir₁/PNbA, and Pt₁/PNbA exhibited outstanding HER performance, and their ΔG_H* values are near the optimal (ΔG_H* → 0). The Co₁/PNbA and Pt₁/PNbA catalysts showed marvelous OER and ORR performance. Co₁/PNbA (0.50/0.35 V) and Pt₁/PNbA (0.50/0.39 V) have significantly lower overpotentials than previously reported OER/ORR catalysts. The Pt₁/PNbA is revealed as a most promising multipurpose electrocatalyst for metal-air batteries and water splitting. Also, the solvation effect demonstrated that Co₁/PNbA, Fe₁/PNbA, and Pt₁/PNbA had reduced overpotentials. Thus, PNbA cluster is suitable for developing highly efficient SACs for HER/ORR, and OER.