Synthesis And Performance Of Composite Electrocatalysts Based On Cerium Dioxide For Oxygen Reduction Reaction

As a safe,efficient,green and renewable new energy technology,fuel cell has important applications in mitigating resource depletion and treating environmental pollution.Oxygen reduction reaction?ORR?is the key reaction of fuel cell,but its slow and complicated kinetic process restricts its development.In the previous work in our group,the nanocomposites containing CeO2 and nitrogen-doped carbon nanocomposites demonstrated excellent ORR catalytic activity owing to their rich active sites and ideal catalytic pathways.Based on this work,iron,sulfides and transition metal oxides were selected to be combined with ceria@nitrogen-doped materials to achieve electrocatalysts,and related electrochemical tests were conducted.The details are as follows:1.Using ferric chloride as oxidant and iron source,sodium dodecylbenzene sulfonate as surfactant,the pyrrole was polymerized on the surface of CeO2 nanospheres to obtain the related products.After further high-temperature carbonization of the synthesized product,CeO2@nitrogen-doped carbon composite materials effectively embedded with iron and sulfur elements?CeO2@Fe,S,N-C?were obtained.The material exhibits excellent ORR catalytic performance.The initial and half-wave potential in 0.1 M KOH solution are 0.924 V and 0.835V relative to the reversible hydrogen electrode?RHE?,respectively,and the limiting current density is 5.450 mA cm^-2 at 0.4 V.The half-wave potential and current density are better than commercial Pt/C.In addition,it also has good stability and excellent resistance to methanol poisoning.After 35,000 s cycling test,the current density of CeO2@Fe,S,N-C showed only 7%loss.The excellent ORR catalytic activity is attributed to the presence of CeO2 and the effective incorporation of iron and sulfur elements in the carbonization process.2.Using CeO2 nanospheres as a carrier and ammonium persulfate as an oxidizing agent,aniline was polymerized on the surface of CeO2 to obtain CeO2@polyaniline.Under room temperature conditions,CeO2@polyaniline and potassium permanganate were further reacted to obtain related products.After further high-temperature carbonization,CeO2@nitrogen-doped carbon composite materials anchored with MnO?CeO2@N-C/MnO?were obtained.This sample presents satisfactory ORR performance.The initial and half-wave potential in 0.1 M KOH solution are 0.920 V and 0.824 V with respect to the reversible hydrogen electrode?RHE?,respectively,and the limit current density is 6.06 mA cm^-22 at a potential of 0.4 V.In addition,it also has good stability and excellent resistance to methanol poisoning.After 25,000 s of cyclic operation,the current density decreased by 13%,while the commercial Pt/C decreased by 23%.The excellent ORR catalytic activity is attributed to the synergistic effect between CeO2,MnO and nitrogen-doped carbon materials.