Promotion of the Electrocatalytic Oxygen Evolution Reaction by Chemical Coupling of CoOOH Particles to 3D Branched γ-MnOOH Rods

Abstract

The chemical-coupled three-dimensional (3D) γ-MnOOH with CoOOH particles (γ-MnOOH/CoOOH) was fabricated through a two-step strategy involving a hydrothermal and reduction–oxidation process. The strong solid–solid interfacial interactions between γ-MnOOH rods and CoOOH particles feature the Mn–O–Co bond on the interface and a high valence state of cobalt in CoOOH. The branched γ-MnOOH/CoOOH composites demonstrate a significantly strengthened synergy effect for the oxygen evolution reaction (OER). The optimal B-MCO-0.1 (γ-MnOOH/CoOOH-0.1) shows an excellent OER performance, which requires an overpotential of 313 mV to reach the current density of 10 mA cm–2 with a lower Tafel slope (87 mV dec–1) and the strong durability in alkaline electrolyte. Specially, the intrinsic OER activity (versus electrochemical active surface area, ECSA) on B-MCO-0.1 at an overpotential of 420 mV is 16.3 and 8.9 times higher than those of γ-MnOOH and CoOOH, respectively. The results demonstrate that OER activity originates mainly from the interfacial coupling of γ-MnOOH and CoOOH. Our work highlights the vital function of the interfacial interactions in modulating the electronic structure of the active sites and suggests an effective avenue to rationally design highly active electrocatalysts.