Hollow mesoporous carbon supported Co-modified Cu/Cu2O electrocatalyst for nitrate reduction reaction

Co-modified Cu/Cu2O catalyst supported on hollow mesoporous carbon substrates (Co/Cu/Cu2O-MesoC) was obtained by a one-step microwave-assisted reduction method and was investigated for electrocatalytic NO3− to NH3. It is found that Co/Cu/Cu2O-MesoC shows a maximal Faradaic efficiency of 100 ± 1% in 0.1 M NO3− at −0.25 V vs. RHE and an excellent NH3 yield rate of 6.416 ± 0.78 mmol mgcat−1h−1 (loading 0.1 mg cm−2) at −0.45 V vs. RHE. In situ Fourier transform infrared spectroscopy reveals the following reaction pathway: NO3− → *NO3 → *NO2 → *NO → *N → *NH → *NH2 → *NH3 → NH3, and indicates that the addition of Co could promote water electrolysis, and the generated H* is involved in the following hydrogenation of intermediates, ultimately leading to faster kinetics and energetics during electrocatalytic conversion of NO3− to NH3. [Display omitted] The electroreduction of nitrate (NO3−) pollutants to ammonia (NH3) provides a sustainable approach for both wastewater treatment and NH3 synthesis. However, electroreduction of nitrate requires multi-step electron and proton transfer, resulting in a sluggish reaction rate. Herein, we synthesized a Co-modified Cu/Cu2O catalyst supported on hollow mesoporous carbon substrates (Co/Cu/Cu2O-MesoC) by a one-step microwave-assisted reduction method. At −0.25 V vs. reversible hydrogen electrode (RHE), Co/Cu/Cu2O-MesoC shows a Faradaic efficiency (FE) of 100 ± 1% in 0.1 M NO3−. Notably, the maximum NH3 yield rate (YieldNH3) reaches 6.416 ± 0.78 mmol mgcat−1h−1 at −0.45 V vs. RHE, which is much better than most of the previous reports. Electrochemical evaluation and in-situ Fourier transform infrared (FTIR) spectroscopy reveal that the addition of Co could promote water electrolysis, and the generated H* is involved in the following hydrogenation of intermediates, ultimately leading to faster kinetics and energetics during electrocatalytic conversion of NO3− to NH3. This synergetic electrocatalysis strategy opens a new avenue for the development of high-activity, selectivity, and stability catalysts.