Synergistic effect to unlock the activity and stability for oxygen evolution reaction in spinel LiMn2O4 via d-block metal substitution

An effective strategy using d-block metal hybridization was proposed to induce electronic interaction and promote the synergistic effect, aiming to enhance the OER performance of cost-effective spinel LiMn2O4. Indeed, we deploy a series of LiNixMn2-xO4 catalysts substituted with Ni, yielding the increase of Mn valence states from Mn3.5+ to Mn4+. The LiNi0.5Mn1.5O4 catalyst achieved an excellent OER performance in alkaline media, with an overpotential reduction more than 320 mV at 10 mA cm-2 compared to the unsubstituted LiMn2O4, as well as the electrochemical stability. It was shown to be superior to most reported Mn-based oxide OER electrocatalysts. Theoretical calculations demonstrated that Ni dopes holes in the Mn site, leading to an increase in Mn4+, and that the shared covalent network of Ni 3d-O 2p-Mn 3d optimized an easier desorption of intermediates. These results pave a new example for modulating the chemisorption strength, thus enabling activating the activity and stability of the OER process for cost-effective electrocatalysts based on spinel Mn oxides.