Nitrogen Electrochemical Reduction Reaction Pathways Evidenced by Online Electrochemical Mass Spectrometry and Isotope Labeling on the MoS<sub>2</sub> Surface
Rodrigo Gomes de Araujo, Joelma Perez
Abstract
High Resolution Image Download MS PowerPoint Slide The electrochemical nitrogen reduction reaction (NRR) for ammonia production is a promising method for mitigating CO 2 emissions. In this study, we investigate the NRR in alkaline media using both labeled and unlabeled compounds on MoS 2 electrodes, employing online electrochemical mass spectrometry (OLEMS) and UV-vis spectroscopy to identify gaseous and solution-phase products, respectively. Notably, OLEMS results reveal the detection of N 2 H + and N 2 H 2 + species as intermediates of the NRR, following the observation of N 2 consumption at −0.4 V vs. RHE and the onset of NH 3 production around −0.5 V vs. RHE. However, N 2 H 3 + and N 2 H 4 + species were not observed. UV-vis spectroscopy confirmed the production of NH 3 . The N 2 molecule first adsorbs onto the catalyst surface, leading to two consecutive protonation steps and the formation of N 2 H and N 2 H 2 intermediates at potentials below −0.4 V. N 2 H 2 is identified as the predominant intermediate in ammonia production. For the first time, this study, utilizing isotope labeling and OLEMS, has enabled the identification of key NRR intermediates, the correlation of NH 3 production with N 2 consumption as a function of applied potential, and has provided crucial insights into this important reaction. A comprehensive understanding of the NRR mechanism will facilitate the development of high-performance catalysts.