MoO2/Ni heterojunction with strong electronic coupling prepared by in-situ phase separation for High-Efficiency nitrate electroreduction to ammonia

Abstract

Further improvements in ammonia selectivity and Faraday efficiency are severely hampered by the complexity of the nitrate reduction process and the intense competitive reaction. Therefore, it is awfully imperative to develop highly active NITRR electrocatalysts and further investigate their catalytic mechanism. In this work, MoO2/Ni cuboids with intimate interfaces were constructed by in-situ phase separation induced strategy for electrocatalytic reduction of nitrate and selective synthesis of ammonia, further expanding the application field of this metallic oxide-metal heterostructure catalyst. The experimental results indicate that the strong interaction between MoO2 and Ni causes the redistribution of interfacial charges, which reasonably explains the extraordinary NITRR activity of MoO2/Ni. In addition, the exposure of numerous active sites at the interface and the amelioration of inherent conductivity are also advantageous for the enhancement of catalytic activity. The theoretical results elucidate the detailed catalytic mechanism. MoO2/Ni showcases lower·NH3 desorption energy and higher hydrogen adsorption energy than pure MoO2 and Ni, which promotes the production of ammonia. In short, the strong electronic interaction between MoO2 and Ni tailors the electronic structure of MoO2/Ni, thus regulating the adsorption energy of the intermediates, and observably improving the FE (95.9%) and ammonia selectivity (96.9%) of MoO2/Ni.