Ammonia and formate cosynthesis via nitrate electroreduction combined with methanol electrooxidation over nitrogen-doped carbon-encapsulated nickel iron phosphide†

Abstract

Nitrate–methanol co-electrolysis involving the cathodic nitrate reduction reaction (NO₃RR) combined with the anodic methanol oxidation reaction (MOR) is a viable way to synchronously produce ammonia (NH₃) and formate via gentle, sustainable and energy-saving “E-refining” and “E-reforming” means. An efficient bifunctional catalyst for the NO₃RR and MOR is pivotal to achieve such a goal. In this work, a nitrogen-doped carbon-encapsulated nickel iron phosphide hybrid (Ni₂FeP@NC) was prepared as a bifunctional catalyst for the NO₃RR and MOR, and its electrochemical performance for nitrate–methanol co-electrolysis was investigated. The Ni₂FeP@NC catalyst exhibited a high NH₃ yield (0.47 mmol h⁻¹ cm⁻² at −0.35 V) and faradaic efficiency (FE, 93% at −0.15 V) for the NO₃RR and simultaneously demonstrated high MOR efficiency for formate production (yield of 1.62 mmol h⁻¹ cm⁻² at 1.7 V and FE of around 95%). The bifunctional catalytic features of the nitrate–methanol co-electrolysis system enabled the concurrent production of NH₃ and formate at low input voltage. This work provides a viable paradigm for pairwise electrosynthesis of valuable chemicals via “E-refining” and “E-reforming” through the rational design of bifunctional catalysts.