Efficient Electrochemical Reduction of CO2 by Ni-N Catalysts with Tunable Performance

摘要

Developing highly selective and durable catalysts for electrochemical CO2 reduction (ECR) to valuable chemicals is essential for curbing CO2 emissions into the atmosphere and to close the anthropogenic carbon cycle. Herein, we report facile and scalable synthesis of Ni/NC as an efficient low-cost catalyst for ECR to CO. The electrocatalytic properties of the catalysts can be readily tailored by tuning N configurations and the fraction of single Ni sites in Ni/NC via manipulation of the N precursor and annealing conditions. The Ni/NC catalyst designed by thermal treatment of a composite mixture of carbon black, Ni(II) acetate, and polyacrylonitrile achieved low overpotential CO2 to CO conversion with a Faradaic efficiency (FE) as high as 96.5% at -0.9 V (vs reversible hydrogen electrode, RHE), a current density reaching -12.6 mA cm(-2) at -1.2 V (vs RHE) corresponding to a CO turnover frequency of up to 4760 h(-1). In addition, high FEs for CO formation (>= 84.7%) were obtained in a wide potential range from -0.8 to -1.2 V (vs RHE) on the Ni/NC electrode. X-ray photoelectron spectroscopy and X-ray absorption near-edge structure spectra in combination with multiple electrochemical results suggested that the pyrrolic N and Ni-N structures concertedly play a determinant role in the catalytic performance of Ni/NC during the CO2 reduction reaction.