Phosphorus-Enhanced Bimetallic Single-Atom Catalysts for Hydrogen Evolution

Single-atom catalysts (SACs), where individual metal atoms are anchored on support, hold great promise for electrocatalytic hydrogen evolution reactions (HERs). The inherent simplicity of the single-atom center restricts opportunities for further enhancement. Binuclear SACs, incorporating two different metal sites, can further improve HER kinetics. However, the underlying mechanisms of the HER at the binuclear sites are complex and not fully understood, hampering the design of new efficient catalyst structures. Here, a comprehensive investigation is presented into phosphorus-doped iron and cobalt bimetallic SACs supported on nitrogen-doped graphitic carbon (P/FeCo-NC), focusing on the potential mechanisms underpinning their enhanced HER activity. P/FeCo-NC exhibits overpotentials of 38 and 95 mV at 10 mA cm² in 0.5 m H₂SO₄ and 1 m KOH, respectively, nearing the acidic performance of commercial Pt/C (33 mV). Theoretical studies reveal that the phosphorus bridge significantly alters the electronic properties of the Fe active sites, while the adjacent Co atoms modulate the electronic environment, further optimizing the hydrogen adsorption-free energy toward more favorable kinetics. This work highlights the structure-activity relationships of bimetallic SACs and opens perspectives for future applications.