Self-supported Fe-doped CoMoO4 nanoarray as high-efficiency electrocatalyst for the electrochemical reduction of nitrite to ammonia

Self-supported Fe–CoMoO 4 /NF nanosheets were fabricated. • The optimized catalyst delivers an ammonia yield of 44.6 ± 0.12 mg −1  cm −2 and high FE of 98.77 ± 0.23% at −0.8 vs. RHE. • The electrocatalytic mechanism was investigated. • Zn- NO 2 − battery with Fe-CoMoO 4 /NF as cathode were tested. The electrochemical reduction of nitrite to ammonia (NO 2 − RR) plays a pivotal role in closing the nitrogen cycle and mitigating nitrogenous pollution. Herein, we report a self-supported, Fe-doped CoMoO 4 nanosheet electrode grown on nickel foam (Fe-CoMoO 4 /NF), via a scalable hydrothermal-immersion strategy. Benefiting from Fe-induced electronic modulation and retention of the robust, hierarchical nanosheet architecture, the optimized Fe-CoMoO 4 /NF delivers an exceptional NH 3 yield of 44.6 ± 0.12 mg h −1  cm −2 with an ultrahigh Faradaic efficiency of 98.77 ± 0.23% at −0.8 V vs. RHE. In-situ differential electrochemical mass spectrometry (DEMS) coupled with density functional theory (DFT) calculation results reveal that NO 2 − reduction on Fe–CoMoO 4 /NF proceeds through nitric oxide-related intermediates, followed by sequential proton-coupled electron transfer steps toward NH 3 formation. When integrated into a Zn−NO 2 − battery, the catalyst enables a remarkable peak power density of 16.9 mW cm −2 , surpassing the performance of most previously reported electrocatalysts for NO 2 − RR. Fe-doped CoMoO 4 nanosheet self-supported on nickel foam enables highly efficient and selective electrocatalytic reduction of nitrite to ammonia, achieving an exceptional NH 3 yield of 44.6 ± 0.12 mg h −1  cm −2 and an ultrahigh Faradaic efficiency of 98.77 ± 0.23% at −0.8 V vs. RHE in neutral solution. Download: Download high-res image (436KB) Download: Download full-size image