Effects of Different Alcohol Solvents on the Micromorphology of MnMoO4 and Their Electrocatalytic Performance in Ammonia Synthesis

Abstract

In recent years, a variety of catalysts have been applied to electrocatalytic nitrogen reduction (NRR). Previous research has shown that in bimetallic catalysis the synergistic effect between the bimetals results in catalytic properties superior to those of monometallic catalysts. In this work, bimetallic oxide MnMoO₄ nanomaterials with different particle sizes were prepared by a solvothermal method, and the effects of different ratios of the solvents (water/ethylene glycol) on the particle sizes of MnMoO₄ and their influence on the NRR performance were systematically investigated. The results showed that as the proportion of ethylene glycol solvent increased, scanning electron microscopy (SEM) characterization showed a transformation of morphology from micrometer-scale rods to nanoscale particles, and the smallest MnMoO₄ particle size was obtained at a water/ethylene glycol ratio of 0:1. Under this condition, the formed MnMoO₄ exhibited excellent NRR properties at −0.40 V vs RHE with an NH₃ yield as high as 21.89 μg h^–1 mg_cat^–1 and a Faraday efficiency (FE) of 15.12%, with the best stability among all catalysts synthesized in this work. This may be attributed to the increased viscosity of the ethylene glycol environment, leading to a deceleration of the precursor reactions. This leads to the production of materials with smaller particle sizes, exposing more active sites and improving catalytic performance. In addition, we explored the effect of other solvents (n-butanol and glycerol) on the morphology of the materials. This work indicates that changing the solvent to regulate the morphology and size of the bimetallic oxide MnMoO₄ can improve the catalytic efficiency of the catalyst, providing a promising electrocatalyst for nitrogen reduction reactions.