Enhancing Low-Concentration Electroreduction of NO to NH3 via Potential-Controlled Active Site-Intermediate Interactions

Xiaoxi Guo; Tongwei Wu; Hengfeng Li; Liyuan Chai; Min Liu

doi:10.1002/anie.202420346

Enhancing Low-Concentration Electroreduction of NO to NH3 via Potential-Controlled Active Site-Intermediate Interactions

Angew Chem Int Ed Engl. 2024 Nov 20:e202420346. doi: 10.1002/anie.202420346. Online ahead of print.

Authors

Xiaoxi Guo¹, Tongwei Wu², Hengfeng Li¹, Liyuan Chai³, Min Liu⁴

Affiliations

¹ Central South University, School of Materials Science and Engineering, CHINA.
² University of Electronic Science and Technology of China, Institute of Fundamental and Frontier Sciences, CHINA.
³ Central South University, School of Metallurgy and Environment, CHINA.
⁴ Central South University, School of Physics and Electronics, 932 Lushan Nan Road, 410081, Changsha, CHINA.

PMID: 39567259
DOI: 10.1002/anie.202420346

Abstract

Electronic defect states in catalysts are recognized as effective active sites for enhancing the low-concentration electroreduction of NO to NH3 (NORR). Their structures dynamically evolve with applied potentials, allowing the active sites to adjust interactions with intermediates, thereby improving electrocatalytic performance. However, the dynamic changes in these interactions under applied potentials remain poorly understood, hindering the design of diverse electrocatalytic systems. Herein, we developed a strategy that unitizes potential to control the interactions between active sites and intermediates over VO-TiO2-x to enhance NORR performance. Combining constant inner potential (CIP) DFT calculations with in situ (spectro)electrochemical measurements, we investigated how the electrode potential influences these interactions in NORR. The results demonstrate that applying external potentials promote the formation of Ti3+ active sites and alter its spatial symmetry of degenerate orbitals to facilitate the generation of key intermediates for NO-to-NH3 conversion. Therefore, the VO-TiO2-x catalyst exhibited superior NORR performance with Faradaic efficiency of 76.4% and NH3 yield rate of 632.9 μg h-1 mgcat.-1 under 1.0 vol% NO atmosphere, which is competitive with reported works under higher NO concentration (above 10 vol%). Remarkably, the NORR process achieved a record-breaking NH3 yield of 2292.7 μg h-1 mgcat.-1 in a membrane electrode assembly (MEA) electrolyzer.

Keywords: NH3 synthesis; O vacancy; electrocatalytic NO reduction reaction (NORR); in situ spectroelectrochemical; low-concentration NO.