The synergetic effect of the mixed phase of NiMoO4 with a 1D–2D–3D hierarchical structure for a highly efficient and stable urea oxidation reaction†
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Abstract
Using a urea oxidation reaction (UOR) instead of an oxygen evolution reaction (OER) is regarded as an effective method for reducing the required hydrogen potential and overall energy costs. Nickel molybdate (NiMoO4) is considered as an efficient UOR catalyst, and its crystalline phase plays a pivotal role in improving the UOR activity. However, a deep understanding of the relevant mechanism of the NiMoO4 phase remains largely ambiguous. Herein, a mixed phase (α/β) of the NiMoO4@NF electrode with a 1D–2D–3D hierarchical structure is fabricated using a facile solvothermal strategy. This unique 1D–2D–3D hierarchical structure is conducive to exposing more abundant active sites. The experiments and density functional theory (DFT) calculations jointly demonstrate that α/β-NiMoO4 can bring “1 + 1 > 2” multiphase synergetic effects, higher conductivity and lower adsorption energy of urea molecules, which is beneficial for improving the UOR performance. Consequently, the α/β-NiMoO4@NF electrode exhibits a decent UOR activity, i.e., at a potential of 1.36 V to reach 100 mA cm−2, about 315 mV less than that of the OER. This study provides a promising method for energy conservation and treatment of urea-containing wastewater.
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