Nano-Polycrystalline Cu Layer Interlaced with Ti<sup>3+</sup>-Self-Doped TiO<sub>2</sub> Nanotube Arrays as an Electrocatalyst for Reduction of Nitrate to Ammonia
Mingfei Chen, Shuxian Zhuang, Jinlu Cheng, Jinyuan Miao, Xuefeng Tai, Yinghua Gu, Zhiwei Qin, Jinpeng Zhang, Yang Tang, Yanzhi Sun, Pingyu Wan
Abstract
The electrochemical nitrate reduction reaction (NO 3 RR) is considered as a promising strategy to degrade nitrate-containing wastewater and synthesize recyclable ammonia at atmospheric pressure and room temperature. In this work, the copper oxides-derived nano-polycrystalline Cu (NPC Cu) was integrated with Ti 3+ -self-doped TiO 2 nanotube arrays (NTA) to fabricate the NPC Cu/H–TiO 2 NTA. Ti 3+ -self-doped TiO 2 NTAs and the NPC Cu facilitate electron transfer and mass transportation and create abundant active sites. The unique nanostructure in which Cu nano-polycrystals interlace with the TiO 2 nanotube accelerates the electron transfer from the substrate to surface NPC Cu. The density functional theory calculations confirm that the built-in electric field between Cu and TiO 2 improves the adsorption characteristic of the NPC Cu/H–TiO 2 NTA, thereby converting the endothermic NO 3 – adsorption step into an exothermic process. Therefore, the high NO 3 – conversion of 98.97%, the Faradic efficiency of 95.59%, and the ammonia production yield of 0.81 mg cm –2 h –1 are achieved at −0.45 V vs reversible hydrogen electrode in 10 mM NaNO 3 (140 mg L –1 )–0.1 M Na 2 SO 4 . This well-designed NPC Cu/H–TiO 2 NTA as an effective electrocatalyst for the 8e – NO 3 RR possesses promising potential in the applications of ammonia production.