Highly efficient electrochemical water splitting is of prime importance in hydrogen energy but is suffered from the slow kinetics at the anodic oxygen evolution reaction. Herein, combining the surface activation with the heterostructure construction strategy, the CoP/Fe-Co 9 S 8 heterostructures as the pre-catalyst for highly efficient oxygen evolution are successfully synthesized. The catalyst only needs 156 mV to reach 10 mA cm −2 and keeps stable for more than 150 h. Inductively coupled plasma optical emission spectrometry, in situ Raman spectroscopy and density functional theory calculations verify that the introduction of Fe can promote the formation of highly active Co(IV)-O sites and lead to a self-termination of surface reconstruction, which eventually creates a highly active and stable oxygen evolution catalytic surface. Besides, the catalyst also demonstrates high hydrogen evolution reaction activity with an overpotential of 62 mV@10 mA cm −2 . Benefiting from its bifunctionality and self-supporting property, the membrane electrode assembly electrolyzer equipped with these catalysts achieves high overall water splitting efficiency of 1.68 V@1 A cm −2 .

The electrochemical oxidation process has the unique advantage of in-situ •OH generation for deep mineralization of organic pollutants, which is expected to provide a solution for the globally decentralized wastewater treatment and reuse. However, it is still a great challenge to develop low-cost anodes with ultrahigh •OH yield and low energy consumption. Here, a low-cost and stable mixed metal oxide (MMO) anode (Cu-Sb-SnO 2 ) developed by a simple and scalable preparation process presents extremely high organic pollutants degradation efficiency and low energy consumption. The tetracycline degradation kinetics constant of the Cu-Sb-SnO 2 system (0.362 min −1 ) was 9 to 45 times higher than that of other prepared anodes, which is superior to the existing anodes reported so far. The experimental results and theoretical calculations indicate that the Cu-Sb-SnO 2 has moderate oxygen evolution potential, larger water adsorption energy, and lower reaction energy barrier, which is conducive to selective water oxidation to generate •OH. Notably, it is systematically and comprehensively confirmed that the generation of •OH triggered by in situ electrogenerated Cu(III) increased •OH steady-state concentration by over four times. Furthermore, the doped Cu species can play a key role in promoting charge transfer as an “electronic porter” between Sn and Sb in the electrocatalytic process by adjusting the electronic structure of the Sb-SnO 2 electrode. This work paves the way for the development of MMO anodes utilizing the advantage of the Cu redox shuttle.

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