Electrochemical synthesis of amorphous metal hydroxide microarrays with rich defects from MOFs for efficient electrocatalytic water oxidation

MOFs featuring adjustable functions show good prospects for creating low-cost oxygen evolution reaction (OER) electrocatalysts, but their poor stability and conductivity seriously limit their real applications. Herein, we report a general in-situ electrochemical approach for the synthesis of amorphous metal hydroxide-based microarrays assembled on nickel foam (NF) by using leaflike CoM-ZIF-L as precursors for boosting OER performance. It is demonstrated that an electrochemical cyclic voltammetry (CV) redox process can promote the ligand substitution of CoM-ZIF-L to afford highly-active amorphous metal hydroxides with abundant oxygen defects via activating the reversible redox of metal ions, removing 2-methylimidazole and subsequently capping OH−. As expected, the optimized aCo(OH)2-ZIF-L/NF can provide rich catalytic sites, good conductivity and short ion diffusion paths, all of which are responsible for its excellent OER activity. Further experiment and DFT calculation results confirm that the in-situ formed defective amorphous metal oxy(hydroxide) is the real active species for this electrocatalytic reaction.