Modification of mesoporous LiMn2O4 and LiMn2−xCoxO4 by SILAR method for highly efficient water oxidation electrocatalysis

Abstract

Iridium, ruthenium, and cobalt oxides are target materials as efficient and stable mesoporous metal oxide electrocatalysts for oxygen evolution reaction (OER). However, they are costly, toxic, and not practical for an efficient OER process. Here, a two‐step method is introduced, based on earth‐abundant manganese; molten salt‐assisted self‐assembly process to prepare mesoporous LiMn2−xCoxO4 (x = 0–0.5) modified electrodes, in which a systematic incorporation of Co(II) into the structure is performed using successive ionic layer adsorption and reaction followed by an annealing (SILAR‐AN) process. Applying SILAR‐AN over a stable m‐LiMn1.6Co0.4O4 electrode improves the OER performance; the Tafel slope and overpotential drop from 66 to 46 mV dec−1 and 304 to 265 mV (at 1.0 mA cm−2), respectively. The performance of the modified electrodes is comparable to benchmark IrO2 and RuO2 catalysts and much better than cobalt oxide electrodes. Electronic interactions between the neighboring Mn and Co sites synergistically amplify the OER performance of the m‐LiMn2−xCoxO4 electrodes. The data are compatible with an eight steps nucleophilic acid‐base reaction mechanism during OER.