A Spectroscopic Study of Electrochemical Nitrogen and Nitrate Reduction on Rhodium Surfaces

Abstract Rh is a promising electrocatalyst for the nitrogen reduction reaction (NRR) given its suitable nitrogen‐adsorption energy and low overpotential. However, the NRR pathway on Rh surfaces remains unknown. In this study, we employ surface‐enhanced infrared‐absorption spectroscopy (SEIRAS) and differential electrochemical mass spectrometry (DEMS) to study the reaction mechanism of NRR on Rh. N 2 H x (0≤ x ≤2) is detected with a N=N stretching mode at ≈2020 cm −1 by SEIRAS and a signal at m / z =29 by DEMS. A new two‐step reaction pathway on Rh surfaces is proposed that involves an electrochemical process with a two‐electron transfer to form N 2 H 2 and its subsequent decomposition in the electrolyte producing NH 3 . Our results also indicate that nitrate reduction and the NRR share the same reaction intermediate N 2 H x .