Construction Of Heterogeneous Interfacial Catalysts And Their Electrocatalytic CO₂ Reduction Performance

Electrocatalytic CO₂ reduction（CO₂RR）,when powered with renewable energies（such as solar and wind）,could produce value-added commodity chemicals.Among of various products,formic acid is the most promising liquid-phase product for practical application.Formic acid is a basic chemical feedstock and an important liquid-phase hydrogen storage material in the electrocatalytic field.Bismuth（Bi）has the advantages of low cost and low toxicity,and its application in CO₂RR shows high formic acid selectivity,but it also suffers from high overpotential,low activity and poor stability in the reaction.The products generated are mixed in the electrolyte in H-type and flow cells,and require subsequent separation and purification processes.Therefore,the synthesis of efficient catalysts and optimization of the electrolytic cell structure are keys to obtaining the products in high concentration.In this paper,Bi/CeO_2–x catalysts with heterogeneous interfaces were synthesized;it exhibited high product selectivity and catalytic activity in CO₂RR,and were applied to a modified membrane electrode electrolytic cell to obtain high-concentration liquid fuels.The main contents are as follows:1.Construction of heterogeneous interface Bi/CeO_2–x catalysts for efficient CO₂RR.The uniform nanosheets of precursor were in situ grown on the carbon fibers,the heterogeneous nanoparticles composed of multiple smaller particles were formed after pyrolysis.The Bi/CeO_2–x heterogeneous interfacial structures were determined by X-ray diffraction（XRD）and transmission electron microscopy（TEM）.Electron paramagnetic resonance（EPR）spectroscopy and X-ray photoelectron spectroscopy（XPS）revealed that Bi/CeO_2–x has more oxygen vacancies,and thus it could be inferred that oxidation of the Bi surface was restrained after Ce modification,which is conducive to the formation of the intermediate for formate.For CO₂RR,the FE_HCOOHof Bi/CeO_2–x reached the maximum of 98.7%at–0.95 V vs.RHE.The long-term stability and corresponding FE_HCOOH were assessed for 120 h at–0.8 V vs.RHE,and the results indicated an excellent stability for CO₂RR with high FE_HCOOH.Furthermore,the j_HCOOH reached to 120 m A cm^–2 at-0.80 V vs.RHE with FE_HCOOH>90%for 28 h.The Bi/CeO_2–x catalyst could help to activate H₂O and CO₂ during CO₂RR,indicating a higher catalytic activity.2.High-concentration formic acid production using Bi/CeO_2–x via membrane electrode assembly（MEA）electrolytic cell.CO₂RR was carried out using a membrane electrode setup with a mixed electrolyte of 0.5 M K₂SO₄ and 0.01 M H₂SO₄ at the anode.Equipped with this catalyst,the MEA cell could produce HCOOH with a concentration as high as 1.30–1.51 M over the voltage range from 2.9to 3.5 V with FE_HCOOH above 90%.The highest formic acid concentration(C_HCOOH)was 1.51 M at 3.2 V.The CO₂RR stability test was carried out over 45 h at 3.03 V,demonstrating no significant decline in both selectivity and current density.The preparation process of this device was simple,which was convenient to reduce the energy consumption and cost in the subsequent product separation and purification process,and it was suitable for large-scale application in the field of electrocatalysis.