Syntheses And Electrocatalytic CO₂ Reductions Of Nickel-based Nanocarbon Hybrid Materials

The overdependence of fossil energy poses a pending threat to humanity due to excessive emission of carbon dioxide(CO2)and energy shortages.Conversion of CO2 into value-added chemicals through electrocatalytic CO2 reduction reaction(CO2RR)is considered as an up-and-coming way to facilitate renewable closed carbon cycle and energy storage.However,multiple proton-electron transfer processes,as well as the concomitant competitive hydrogen evolution reaction,are always happening during the CO2RR.Many chemists painstakingly hunt for robust,stable and low-cost electrocatalysts,which is significant for the promotion and application of CO2RR.Making full use of the interaction between metal and carrier electrons will help design high-efficiency CO2RR electrocatalysts.Based on transition metal nickel(Ni)and the Ni-N-C structure,efficient and inexpensive nickel-carbon composites are designed and synthesized in this paper.The main contents are as follows:1.Nickel ultrafine nanoparticles were in-situ coated in the bamboo-shaped carbon nanotubes by one-step pyrolysis of nickelnitrate and melamine.Remarkably,the asprepared catalyst NiN3 electrically catalyzed CO2 into CO with a Faradaic Efficiency of 96.5%at-0.7V vs.reversible hydrogen electrode(RHE)and delivered excellent stability over 27 hours with negligible current density lost.The sizes of these Ni moieties are ranging from single atom level to 10 nm,which possessed high proportion of under coordinated surface atoms and active sites.By balancing the relationship of size and performance,this work provided a new scope to facilely prepare robust and low-cost Metal-N-C hybrid electrocatalysts for CO2 reduction reaction.2.A Ni single-atom catalyst(Ni-SAs-NC)was successfully prepared via the facile precursor assembly strategy and the subsequent one-step pyrolysis process.Characterizations demonstrate that abundant Ni single-atom active sites with the coordination structure of Ni-N4 are uniformly dispersed in Ni-SAs-NC,which consequently endow it with outstanding electrocatalytic CO2RR performance.Strikingly,the as-prepared Ni-SAs-NC can selectively convert CO2 into CO with a high Faradaic efficiency up to 98%at-0.65V,and can maintain the high values exceeding 90%in a wide potential range from-0.6 to-1.0 V.This work provides a new protocol to prepare high-efficiency but low-cost single-atom electrocatalysts toward CO2RR and other electrochemical reactions.