Precision N-species engineering in Pt–N4via ring reconstruction towards efficient alkaline water electrolysis

Abstract

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 the stabilities and activities of Pt–N₄–C, a leading hydrogen evolution catalyst. Guided by 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 Co_n 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 catalysts.