Boosting electrocatalytic activity of 3d-block metal (hydro)oxides by ligand-induced conversion.

The 3d transition metal (hydro)oxides belong to a group of highly efficient, scalable and inexpensive electrocatalysts for widespread energy-related applications, which feature well-tailorable crystal and electronic structures. We hereby propose a general strategy to further boost their electrocatalytic activities by introducing organic ligands into the framework, in consideration of most 3d metal (hydro)oxides usually exhibit quite strong binding with reaction intermediates and thus compromised activity due to the scaling relations. Involving weakly bonded ligands effectively downshifts the d -band center, which on one side narrows the band gap and on the other side optimizes the adsorption of these intermediates. As an excellent paradigm, the oxygen evolution reaction (OER) activity can be greatly promoted by ~ 5.7 times over a NiCo layered double hydroxide (LDH) after a ligand of terephthalic acid (TPA)-induced conversion process, arising from the reduced energy barrier of the deprotonation of OH* to O*. Impressively, the proposed ligand-induced conversion strategy is applicable to a series of 3d -block metal (hydro)oxides, including NiFe 2 O 4 , NiCo 2 O 4 , and NiZn LDH, providing a general structural upgrading scheme for existing high-performance electrocatalytic systems.