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.