Abstract

The oxygen evolution reaction (OER) is crucial in water electrolyzers and metal-air batteries, but its slow kinetics demand efficient electrocatalysts. 2D coordination polymers offer structural and electronic advantages, making them strong candidates. In this study, we systematically investigate the OER activity of four 2D dicyanidometallate-based Hofmann-type coordination polymers (HCPs), {M(4acpy)(2)[Ag(CN)(2)](2)}(n) (M = Mn, Fe, Co, and Ni; 4acpy = 4-acetylpyridine), denoted as M-Ag. The M-transition metals were strategically selected based on their periodic electronegativity and 3d electronic configuration to explore structure-activity relationships. Our findings reveal a periodic trend in catalytic activity: Ni-Ag > Co-Ag > Fe-Ag > Mn-Ag, with Ni-Ag demonstrating superior activity, surpassing the benchmark RuO2 by 89 mV at 100 mA cm(-2). The superior activity of the Ni-Ag is attributed to a partial surface structural reconstruction induced by the alkaline electrolyte and the applied anodic potential. Experimental results, supported by DFT calculations, indicate an adsorption-driven OER mechanism initiated by the formation of surface Ni-hydroxide species with optimized adsorption energy, which enhances catalytic activity. Under applied potential, these species convert into Ni(III)-OH, whose high acidity facilitates the proton-coupled electron transfer process, accelerating the reaction kinetics. As a pioneering study, this work demonstrates, for the first time, the tunability of M-Ag HCPs, enabling fine control over their OER catalytic performance. Moreover, it introduces the DFT-derived coordination-induced bond weakening (CIBW) effect as a new descriptor for O-H activation, providing new insights into electrocatalyst design. These findings pave the way for the rational development of 2D M-Ag coordination polymers as next-generation OER catalysts for operando applications.