Electroreduction of Nitrogen on Pd, Rh, and PdRh Catalysts: An Online Mass Spectrometry Study

The nitrogen electroreduction reaction (NRR) has emerged as a promising and sustainable alternative to the Haber–Bosch process for NH3 production. This study investigated the NRR in alkaline medium using Pd/C, Rh/C, and PdRh/C electrocatalysts, employing online electrochemical mass spectrometry (OLEMS) for gaseous-product detection and ultraviolet–visible spectroscopy to confirm NH3 formation. To our knowledge, no previous reports have simultaneously detected H2, N2H, and N2H2 intermediates and monitored N2 consumption as a function of applied potential for Pd and Rh catalysts. The bimetallic PdRh/C catalyst showed superior NRR performance compared with the monometallic catalysts, exhibiting higher faradaic charges, more pronounced generation of nitrogen intermediates, and selectivity for NH3. This work provides key insights into the NRR mechanisms and underlines the strategic importance of the bimetallic catalyst design for more efficient, sustainable electrochemical NH3 synthesis.