Construction of built-in electric field in Ru/Vo-NiCo2O4 heterostructure for efficient ethylene glycol oxidation reaction coupled nitrate to ammonia electrolysis

Electrocatalytic nitrate-to-ammonia reduction (NO 3 RR) offers a sustainable alternative to fossil-fuel-dependent Haber-Bosch processes. However, limited NH 3 yield and unsatisfactory faradaic efficiency hindered the development of NO 3 RR. Herein, a unique Ru/V o -NiCo 2 O 4 heterostructure is reported as an effective NO 3 RR catalyst, in which the NiCo 2 O 4 site preferentially adsorbs nitrate, while the Ru site provides active H species for the subsequent reduction process. Structural characterization reveals that enrichment of ruthenium on the surface of nickel-cobalt oxide catalysts by electrochemical deposition not only promotes the generation of abundant oxygen vacancies, but also promotes the charge redistribution and the formation of built-in electric field inside the catalysts, which improves the electrical conductivity as well as promotes the generation of a large number of active sites in the NO 3 RR and EGOR processes. Ru/V o -NiCo 2 O 4 exhibits excellent bifunctional catalytic activity for NO 3 RR and ethylene glycol oxidation reaction (EGOR). Specifically, in the electrocatalytic nitrate reduction for ammonia production, the Faraday efficiency reached up to 95.14 % with an ammonia yield of 17.20 mg h −1 cm −2 at - 0.3 V. The catalyst also performed well for the oxidation of ethylene glycol, with a voltage of only 0.469 V required to achieve a current density of 50 mA cm −2 . After continuous electrolysis for 12 h at a current density of 100 mA cm −2 , the formate Faraday efficiency reaches as high as 88 %. Moreover, utilization EGOR instead of OER to form NO 3 RR||EGOR full cell not only realize energy-saving NH 3 production, meanwhile achieving value-added formate product. For the constructed NO₃RR||EGOR full cell, its formate Faraday efficiency reaches up to 94 % after continuous electrolysis for 12 h at a current density of 100 mA cm −2 . This work provides a strategy to achieve highly efficient, energy-saving ammonia synthesis via rational design of bifunctional electrocatalysts and construction of a co-electrolysis system, which carries substantial significance for both energy and environmental sectors.