Boosting NH production from nitrate electroreduction electronic structure engineering of FeC nanoflakes

• Published in: Green chemistry : an international journal and green chemistry resource : GC 2021-10, Vol.23 (19), p.7594-768
• Main Authors: Wang, Yuanyuan, Zhang, Linlin, Niu, Yongjian, Fang, Dong, Wang, Jiao, Su, Qingxiao, Wang, Cheng
• Format: Article
• ISSN: 1463-9262; 1463-9270
• DOI: 10.1039/d1gc01913a

Clear structure-performance relationships are helpful for the design of efficient catalysts and the understanding of reaction mechanisms. The electrocatalytic nitrate reduction reaction (NO 3 RR) offers a sustainable route to ammonia (NH 3 ) synthesis and nitrate mitigation. However, it suffers from poor nitrate adsorption, low NH 3 selectivity and sluggish reaction kinetics. Herein, N-doped carbon nanosheets supported Fe 3 C nanoflakes featuring large surface areas (860.024 m 2 g −1 ) were prepared. Their NO 3 RR performances showed volcano-like relationships with the Fe 3+ /Fe 2+ ratios and d-band centers. At −0.5 V, the NH 3 yield, faradaic efficiency, selectivity and current density reached 1.19 mmol h −1 mg −1 , 96.7%, 79.0% and 85.6 mA cm −2 , respectively, exceeding most reported results. Such exceptional performances mainly originated from the optimized electronic structures that boosted nitrate adsorption and reaction kinetics (Tafel slope: 56.7 mV dec −1 ). Mechanistic investigations revealed a NO 3 − → NO 2 − → NH 3 reaction pathway with the chemical process following the fast electron transfer process as the rate-determining step. Optimized electronic structures of Fe 3 C/NC boosted NH 3 production from nitrate electroreduction, which proceeded via a stepwise NO 3 − -NO 2 − -NH 3 pathway.