Bioinspired Ruthenium–Porphyrin Electrocatalysts with Atomic N₄/N₂ Proximal Sites for Efficient Proton-Coupled Electron Transfer in Water Electrolysis

Mimicking the proton-coupled electron transfer (PCET) pathways of natural enzymes, we engineer a porphyrin-based ruthenium coordination polymer (Ru-PCPN) with precisely positioned atomic-level N₄/N₂ proximal sites through molecular-scale coordination engineering. This bioinspired architecture establishes a dual-site relay mechanism where the Ru-N₂ center accelerates water dissociation kinetics while the adjacent Ru-N₄ site optimizes hydrogen recombination. Experimental and theoretical results reveal that the sub-nanometer-proximate N₄/N₂ sites function as proton donor-acceptor pairs, enabling directional proton transfer via PCET and synergistically enhancing water electrolysis. When integrated with carbon substrates, the Ru-PCPN@CB catalyst demonstrates exceptional hydrogen evolution performance in alkaline conditions, achieving a low overpotential at 10 mA cm^-2 (42 mV, comparable to 44 mV of Pt/C), high mass activity and TOF of 9.02 A mg^-1 and 4.73 s^-1 (∼7.0 and 3.6 times of Pt/C), and good stability. This work establishes atomic-scale coordination proximity as a new paradigm for breaking scaling relationships in multistep electrocatalysis.