Precision N-Species Engineering in Pt–N4 via Ring-Reconstruction towards Efficient Alkaline Water Electrolysis

Pyridinic-N (N[6]) and pyrrolic-N (N[5]) are vital for the performance of metal-nitrogen-carbon (M–N–C) catalysts, yet precise control over them remains elusive. Here we theoretically explore the impact of N[5]/N[6] atomic ratios on stabilities and activities of Pt–N4–C, a leading hydrogen evolution catalyst. Guided by the insight, we successfully synthesize the Pt–N4–C with an optimized 1:1 N[5]/N[6] ratio via hydrogen-assisted pyrolysis of ZIF-8@ZIF-67, followed by Pt coordination. In-situ generated Co nanoparticles convert partial N[6] to N[5], inducing a ring-reconstruction and fine-tuning of N ratios. The internal N-engineering of Pt1 coordinated with N[5]/[6]C and external OH adsorption on Con significantly reduce the alkaline water splitting energy barrier, achieving an exceptionally low voltage (1.82 V) and excellent stability (400 h @ 1 A cm-2) in membrane electrode assemblies. This work offers crucial insights into optimizing N[5]/N[6] ratios to enhance the performance of M–N–C catalyst.