High-spin transition metal atoms drive acidic oxygen evolution reactions

Synthesizing transition metal catalysts to replace precious metal ones such as IrO₂ and RuO_2, achieving efficient acidic oxygen evolution reaction while balancing intrinsic activity, stability, and cost-effectiveness always been a dream pursued by scientists and industrialists, but still remains a challenge. Here, we present an efficient catalytic system formed by graphdiyne-induced high-spin state cobalt-based oxide (HSS-CoO_x/GDY) for enhancing the activity and stability of the acidic oxygen evolution reaction. Experimental and theoretical results demonstrate that the bonding of electron-rich sp-hybridized carbon and Co atoms initiates the Jahn-Teller effect of CoO₆ octahedra, which regulates the occupied d-orbital of Co atoms and generates the high-spin Co³⁺. Such spin occupancy breaks the spin-forbidden effect and optimizes the adsorption/desorption ability of HSS-CoO_x/GDY toward key reaction intermediates, thereby promoting the coupling of O-O bonds and the evolution of oxygen gas. The proton exchange membrane water electrolyzers constructed based on this catalyst achieve a current density of 1.0 A cm^-2 at a low cell voltage of 1.80 V. This research indicates that graphdiyne has the ability to manipulate the electronic spin states of electrocatalysts.