Spatial configuration of Fe-Co dual- sites boosting catalytic intermediates coupling toward oxygen evolution reaction

Oxygen evolution reaction (OER) is the pivotal obstacle of water splitting for hydrogen production. Dual - sites catalysts (DSCs) are considered exceeding single - site catalysts due to the preternatural synergetic effects of two metals in OER. However, appointing the specific spatial configuration of dual - sites toward more efficient catalysis still remains a challenge. Herein, we constructed two configurations of Fe-Co dual- sites: stereo Fe-Co sites (stereo - Fe - Co DSC) and planar Fe-Co sites (planar - Fe - Co DSC). Remarkably, the planar - Fe - Co DSC has excellent OER performance superior to stereo - Fe - Co DSC. DFT calculations and experiments including isotope differential electrochemical mass spectrometry, in situ infrared spectroscopy, and in situ Raman reveal the *O intermediates can be directly coupled to form *O-O* rather than *OOH by both the DSCs, which could overcome the limitation of four electron transfer steps in OER. Especially, the proper Fe-Co distance and steric direction of the planar - Fe - Co benefit the cooperation of dual sites to dehydrogenate intermediates into *O-O* than stereo - Fe - Co in the rate- determining step. This work provides valuable insights and support for further research and development of OER dual - site catalysts.