| Electrocatalytic carbon dioxide reduction technology is an effective way to fix and utilize CO2,which is of great significance for alleviating global warming and energy crisis.Although scientists have done a lot of work in this field,more efficient CO2 reduction systems have to be developed.This paper focuses on the key problems of electrochemical CO2 reduction,such as Low energy efficiency,high overpotential and poor selectivity.From the two aspects of shape optimization and doping non-metallic atoms,we put forward a new strategy of efficient production of formic acid,and effectively improve the production efficiency of formic acid Faradaic.A flow cell signific-antly increased the current density and to improve the stability of the catalyst.The self-supported electrode of Bi-NAs(bismuth nanosheet arrays)were in situ grown on carbon paper by potentiostatic deposition,which can be directly used as the cathode of CO2RR.Bi-NAs uniformly grow on the skeleton of carbon paper(CP)substrate,which is a kind of interwoven nanosheets growing vertically on carbon paper.The evenly formed gap of nanosheets is conducive to the adsorption of carbon dioxide molecules and shortens the diffusion path of electrolyte in the process of CO2RR.Bi-NAs can efficiently convert CO2 to formic acid,and have high formic acid selectivity and excellent inhibition of hydrogen evolution reaction.Faradic efficiency of formic acid production is up to 95.88%in a wide potential window(-0.85～-1.15 V)(vs.RHE).The electrocatalytic property was further tested using a mobile cell and gas diffusion electrode,the Bi-NAS catalyst was in a 1.0 M KOH electrolyte.When the applied potential was-1.2 V(vs.RHE),the current density reached 213 mA cm-2,meeting the requirements for commercialization(≥200 mA).The selectivity of formic acid selectivity was 92.65%at-0.93 V 1.0 M KOH electrolyte(vs.RHE)and 93.54%at-0.96 V(vs.RHE).Moreover,the average Faradaic efficiency of formic acid was 94.21%when the current reached 213 mA cm-2 for 7 hours.The two-dimensional nanosheet array structure not only promotes electron transfer in the electrode material,but also ensures sufficient active sites for the electrocatalytic reduction of carbon dioxide(eCO2RR)to produce formic acid.Bismuth citrate as bismuth precursor,nitrogen doped bismuth nanosheet woa prepared with calcium hydroxide and ammonium chloride as activator and nitrogen source.The nitrogen doped bisth nanosheet was loaded on the carbon paper(N-Bi/CP)as the cathode material for electrocatalytic CO2RR,nitrogen doped bismuth nanosheet exhibits improved electrical conductivity of the catalyst.This will compensate for the poor electrical conductivity of bismuth-based materials.The catalyst showed excellent electrocatalytic activity and selectivity in electrocatalytic reduction of carbon dioxide.The current density of N-Bi/CP at-1.2 V(vs.RHE)reaches about 50 mA cm-2,and the Faradaic efficiency of formic acid production reaches 94.24%.Importantly,in the flow cell system,a high current density of 318 mA cm-2 was generated at-1.2 V(vs.RHE)and stability was maintained for more than 14 h.An average Faradaic efficiency of 90.86%for formic acid production,indicating that the catalyst remained remarkably stable at high current densities.At the same time,its simple preparation method also makes the catalytic material has great potential for industrialization.The doping of nitrogen can effectively improve the electron density at the edge of Bi nanosheet material,which reduces the energy barrier generated by the intermediate product*COOH,and increase the electrocatalytic activity of the material.The synergistic ability of bismuth and nitrogen also enhances the reaction effect of the catalyst,which may be due to the dislocations,ladder surface and boundary defects introduced by nitrogen,which change the active area and energy/electron density distribution of the catalyst,thus improving the electrocatalytic performance. |
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