Tuning product selectivity in direct electroreduction of NO via phase engineering of MoS2 nanosheets in a water-fed PEM electrolyzer

Abstract

Electrochemical conversion of NO from gaseous pollutants into ammonia using abundant and cost-effective catalyst materials holds great promise for pollutant abatement and for advancing a more closed, sustainable nitrogen cycle. However, regulating product selectivity remains challenging because NO reduction involves complex multielectron/proton pathways. Here, we report two different crystal phases of MoS₂ (2H and 1T′) exhibiting prominent activity in the electrochemical NO reduction reaction (NORR), but showing different selectivities. The faradaic efficiency of ammonia reaches 86% over 2H-MoS₂, outperforming 1T′-MoS₂ (31%) at 2.1 V. In contrast, 1T′-MoS₂ displays higher selectivity towards N₂, especially at a lower cell voltage (50% at 1.7 V). Kinetic and spectroscopic analyses further suggest phase-dependent rate-control characteristics, consistent with distinct pathway preferences on 1T′ versus 2H. Overall, these results demonstrate that NORR activity and selectivity can be efficiently tuned by choosing the appropriate MoS₂ phase, providing a simple strategy to tune product selectivity in complex multistep reactions.