The molten-salt assisted self-assembly (MASA) process is applicable to fabricate high quality mesoporous metal lithiate thin films that exhibit excellent performance as electrocatalysts for water oxidation.
The oxygen evolution reaction (OER) is the bottleneck of the electrochemical water-splitting process, where the use of porous metal oxide electrodes is beneficial. In this work, we introduce a one-pot synthesis method to fabricate a series of mesoporous metal cobaltite (m-MCo 2 O 4 , M = Mn, Ni, and Zn) electrodes for the OER. The method involves preparation and coating of a homogeneous clear solution of all ingredients (metal salts and surfactants) over a fluorine-doped tin oxide surface as a thin lyotropic liquid crystalline film and calcination (as low as 250 °C) to obtain a 400 nm thick crystalline m-MCo 2 O 4 electrode with a spinel structure. Mesophases and m-MCo 2 O 4 films are characterized using structural and electrochemical techniques. All electrodes are stable during the electrochemical test in 1 M KOH aqueous solution and perform at as low as 204 mV overpotential at 1 mA/cm 2 current density; the m-MnCo 2 O 4 electrode works at current densities of 1, 10, and 100 mA/cm 2 at 227, 300, and 383 mV overpotentials after compensating the IR drop, respectively. The Tafel slope is 60 mV/dec for the m-NiCo 2 O 4 and m-ZnCo 2 O 4 electrodes, but it gradually increases to 85 mV/dec in the m-MnCo 2 O 4 electrode by thermal treatment, indicating a change in the OER mechanism.
A molten salt assisted self-assembly method has been employed to produce mesoporous nickel oxide thin films that have a large surface area, efficient water oxidation electrocatalytic performance and good electrochromic properties.
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.
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