The Cu─O─Co Asymmetric Bimetallic Sites Constructed by Ion-Exchange for Efficient Oxygen Evolution Reaction

Recently, constructing oxygen-bridged asymmetric bimetallic sites has proven to be an effective strategy for enhancing electrocatalytic activity. The strong electronic interaction between the metals regulates the d-band center, optimizing the adsorption and desorption of oxygen intermediates and lowering the oxygen evolution reaction (OER) energy barrier. However, examples of constructing such asymmetric sites in π-d conductive metal-organic frameworks (cMOFs) are still scarce. Here, the Co/Cu-DBC (DBC = Dibenzo-[g,p]chrysene-2,3,6,7,10,11,14,15-octaol) with high crystallinity and asymmetric Cu─O─Co bimetallic sites are prepared using an ion-exchange method. By varying the reaction temperature and time, the metal content can be precisely controlled. The Co/Cu-DBC shows excellent OER activity, with a small overpotential of 251 mV at 10 mA cm^-2. Both experimental and density functional theory (DFT) calculations indicate that the construction of asymmetric Cu─O─Co sites leads to strong electronic interactions between Cu and Co through the axial oxygen atom, which regulates the d-band center energy (E_d) level and electronic structure to optimize the adsorption of intermediates and facilitate the formation of ^*O intermediates on the active Co sites toward fast OER kinetics. This work provides new insights for the synthesis and the design of efficient OER catalysts.