A nanoflower-on-nanowire heterogeneous electrocatalyst for enhanced interfacial water activation in nitrate reduction reaction
Jingwen Yu, Yunliang Liu, Cunhao Fan, Naiyun Liu, Jingya Yin, Yaxi Li, Yuanyuan Cheng, Xinya Yuan, Xinyue Zhang, Yixian Liu, Sanjun Fan, Lei Xu, Haitao Li
Abstract
Electrocatalytic nitrate reduction reaction (NitRR) is an efficient route for simultaneous wastewater treatment and ammonia production, but the conversion of NO<sub>3</sub><sup>–</sup> to NH<sub>3</sub> involves multiple electron and proton transfer processes and diverse by-products. Therefore, developing ammonia catalysts with superior catalytic activity and selectivity is an urgent task. The distinctive electronic structure of Cu enhances the adsorption of nitrogen-containing intermediates, but the insufficient activation capability of Cu for interfacial water restricts the generation of reactive hydrogen and inhibits the hydrogenation process. In this work, a Ce-doped CuO catalyst (Ce<sub>10</sub>/CuO) was synthesized by <i>in situ</i> oxidative etching and annealing. The redox of Ce<sup>3+</sup>/Ce<sup>4+</sup> enables the optimization of the electronic structure of the catalyst, and the presence of Ce<sup>3+</sup> as a defect indicator introduces more oxygen vacancies. The results demonstrate that Ce<sub>10</sub>/CuO provides an impressive ammonia yield of 3.88 ± 0.14 mmol·cm<sup>–2</sup>·h<sup>–1</sup> at 0.4 V vs. reversible hydrogen electrode (RHE) with an increase of 1.04 mmol·cm<sup>–2</sup>·h<sup>–1</sup> compared to that of pure CuO, and the Faradaic efficiencies (FE) reaches 93.2% ± 3.4%. <i>In situ</i> characterization confirms the doping of Ce facilitates the activation and dissociation of interfacial water, which promotes the production of active hydrogen and thus enhances the ammonia production efficiency.