A Cascade Jet Plasma Oxidation─electroreduction System Using Pd‐Ni Dual‐Site Catalyst for Sustainable Ammonia Production from Air

Abstract

Electrocatalytic N2 reduction reaction (eNRR) has been deemed as an alternative approach to the Haber‐Bosch (H‐B) process for ammonia (NH3) production, but it remains a huge challenge. Here jet plasma oxidation of N2 is reported in air into NOx and subsequently NO2− coupling with electrochemical NO2− reduction reaction (pN2─eNO2−RR) over PdNi alloying nanoparticles on N‐doped carbon nanotubes (PdNi/N‐CNTs) for NH3 synthesis. The results demonstrate that the jet plasma reactor possesses excellent gas reforming capacity to achieve the largest NO2− yield rate of 30.46 mmol h−1 with a low energy consumption of 2.66 kWh molN−1. For subsequent eNO2−RR, PdNi/N‐CNTs can afford an NH3 yield of 34.96 mg h−1 mgcat.−1 and a faradaic efficiency (FE) of 98.21% at −0.38 and 0.02 V (vs RHE), respectively. In situ spectroscopic characterizations combined with theoretical calculations unveil that PdNi/N‐CNTs provide Pd and Ni dual active sites, enabling NO2− activation on the Ni site and active H* provision on the Pd site to facilitate eNO2−RR. A cascade pN2‐eNO2−RR system is constructed for sustainable NH3 production, achieving a stable NH3 yield rate of 25.56 mmol h−1, an average FE >85%, as well as NOx to NH3 conversion efficiency of 44.62% at constant ampere‐level current with finally collection of gram‐level (NH4) 2SO4 product.