Maximizing Available Active Hydrogen on FeNi Substitutional Solid-Solution Alloy to Boost Electrosynthesis of Ammonia from Nitrate
Xing Sun, Yanzheng He, Mengfan Wang, Qiyang Cheng, Yunfei Huan, Sisi Liu, Jie Liu, Tao Qian, Chenglin Yan, Jianmei Lu
Abstract
Electrochemical nitrate reduction reaction (NO 3 RR) stands out as a promising route for sustainable ammonia synthesis, in which active hydrogen (*H) plays a crucial role in both the deoxygenation and hydrogenation steps. However, the regulation of surface *H is still overlooked, and without intervention, the competing hydrogen evolution reaction is kinetically more favored over the NO 3 RR, leaving the current system as far from satisfactory. Herein, based on reverse utilization of the Sabatier principle, a series of Fe x Ni y substitutional solid-solution alloys (SSAs) are synthesized to manipulate *H behavior for enhanced NO 3 RR. Upon precise optimization of the alloy composition, the d-band center of HER-active Ni shifts toward the Fermi level, endowing the catalyst with strong interaction to *H and greatly prolonging its lifetime, which enables abundant supply to facilitate the NO 3 RR. As expected, a maximum NH 3 yield rate of 31.46 mmol h –1 mg –1 is delivered over the optimized Fe 3 Ni 1 –SSA, which is considerably higher than most of the extensively reported works. Several in situ characterizations are combined to gain in-depth insight. Especially, in situ Fourier transform infrared spectroscopy in internal reflection mode directly observes *H enrichment on the catalyst surface, while the accompanied facilitation of the NO 3 RR process is verified by external reflection mode.