RESUMEN
Electrochemical nitrate reduction to ammonia (NRA) is a promising approach to remove environmental pollutants while producing green NH3 under ambient conditions. Ag-based nanomaterials have been used in NRA but their iron series elements (Fe, Co, Ni) doping has not been explored yet. Herein, an effective and versatile doping strategy of Ag nanocrystals by iron series elements for efficient NRA is presented. Experimental results show that doping with Fe, Co or Ni can improve the NRA activity. Among the catalysts, AgCo delivers the best performance with a Faraday efficiency (FE) of 88.3 % and ammonia selectivity of 97.4 % at-0.23â V vs RHE, which is 1.9 and 6.2 times higher than that of plain Ag (46.4 % FE and 15.8 % selectivity), respectively. A highest NO3 - conversion rate of AgCo (91.8 %) is achieved, which maintains 16.4â ppm NO3 --N in 4â hours, meeting the drinking water level (~15â ppm NO3 --N). Moreover, the FE, selectivity, conversion rate of AgCo do not decay after the four consecutive cycles. It is found that Co doping can effectively induce the change of Ag d-band center for optimized NRA. This work reveals doping effects of iron series elements on Ag-based catalysts, and shows potential practical application in NRA.
RESUMEN
It is of significance to design catalysts for achieving high-performance electrochemical nitrate reduction to ammonia (NRA) in mild neutral media. However, the faradaic efficiency and selectivity are still far from satisfactory. Here, the fabrication of an efficient catalyst was achieved by rationally doping Fe to Cu into a metasequoia-like nanocrystal of CuFe for NRA in neutral media. Fe doping was found to deepen energy level of the Cu 3d band, favorably tuning adsorption energies of reaction intermediates to promote the NRA. At an applied potential of -0.7â V vs. the reversible hydrogen electrode, the CuFe with approximately 2 % Fe doping content delivered a catalytic current density of 55.6â mA cm-2 , which was 2.1â times that of the Cu material. The CuFe also exhibited a faradaic efficiency up to 94.5 %, and a good selectivity of 86.8 %.