Reinforcing built-in electric field via weakening metal–oxygen covalency within MOFs-based heterointerface for robust oxygen evolution reaction

Achieving enhanced built-in electric field (BEF) is highly desirable for accelerating charge transfer and boosting catalytic activity towards oxygen evolution reaction (OER) but still remains a huge challenge. Herein, we constructed the heterointerface composed of FeCo2S4 and CoFe-MOF with abundant oxygen vacancies on Ni foam substrate (named as FeCo2S4@Ov-CoFe-MOF/NF). Experimental and theoretical findings proposed that the introduction of abundant oxygen vacancies into the heterointerface could increase the energy level difference of the two components and reduce electron clouds overlap between metal Co/Fe and oxygen for increased BEF. Such enhanced BEF could accelerate the electronic migration for optimizing the d-band center and adsorption/desorption capacity of reaction intermediates. As expected, the target FeCo2S4@Ov-CoFe-MOF/NF with high BEF intensity displayed splendid OER activity and durability in the alkaline and neutral medium. The present work provides precise guidance for designing other advanced catalysts through deliberately manipulating the BEF.