Promoting the activation of H2O via vacancy defects over metal-organic framework-derived cobalt oxide for enhanced oxygen evolution.

Engineering the electronic structures of transition metal oxides via vacancy defects is an efficient approach to enhance their catalytic performances, while facilely creating vacancy defects and deeply exploring the effects still remain challenging. Herein, a facile reduction method was applied to introduce oxygen vacancy defects into metal-organic frameworks (MOFs)-derived cobalt oxide (Co 3 O 4) polyhedron. Using zeolitic imidazolate framework-67 (ZIF-67) as Co source and self-sacrificial template, Co 3 O 4 with polyhedron morphology and porous structure was synthesized, and then oxygen vacancy defects were introduced into the as-prepared Co 3 O 4 through one-step NaBH 4 reduction treatment. Strikingly, the obtained electrocatalyst (denoted as Co 3 O 4-x) exhibited a larger current density (112.9 mA cm−2 vs. 1.75 V), a lower overpotential (335 mV at 10 mA cm−2) and a smaller Tafel slope (83 mV dec−1) than the Co 3 O 4 , which is even superior to the state-of-the-art IrO 2 catalyst. Moreover, experiment results combined with density-functional theory (DFT) calculations revealed that the existence of oxygen vacancies could improve the conductivity, promote the activation of H 2 O and reduce the potential of potential-limited step (PLS), thus greatly boosting electrocatalytic oxygen evolution reaction (OER) performances. This work reported a strategy for preparing defect-rich OER electrocatalysts, and also provided a deep understanding of the defect effects on catalytic performances. The electronic structures of metal-organic framework-derived Co 3 O 4 polyhedron have been regulated by oxygen vacancy defects and as-prepared Co 3 O 4-x electrocatalysts exhibited enhanced performances for OER. [Display omitted] • Oxygen vacancy defects have been introduced into MOFs-derived Co 3 O 4 polyhedron to enhance OER performances. • As-Prepared Co 3 O 4-x exhibited much better performance than Co 3 O 4 , which is even superior to the state-of-the-art IrO 2. • DFT revealed oxygen vacancies could improve the conductivity, promote H 2 O activation and reduce PLS potential. [ABSTRACT FROM AUTHOR]