Research On Automotive Fuel Cells Based On Co-based Ruthenium-containing Catalyst Cathode

As the car ownership of our country continues to increase rapidly,oil consumption increases accordingly,and the energy crisis and environmental pollution problems are becoming more and more serious.Fuel cells have the advantages of high energy conversion efficiency,low noise,and low environmental pollution.The widespread application of fuel cells in automobiles will greatly alleviate the energy crisis and environmental pollution problems.At present,proton exchange membrane fuel cell（PEMFC）is widely used in fuel cell vehicles because it can operate in low temperature environments,use air as an oxidant,and have mature technologies.However,PEMFC has long been restricted by the high cost and poor durability of the precious metal Pt catalyst,making fuel cell vehicles too expensive to be widely used.Anion exchange membrane fuel cell（AEMFC）,which has a similar principle to PEMFC,has more choices of cathode catalysts because the exchange membrane is an alkaline environment.Among many non-Pt cathode catalysts,Co-based oxides have attracted much attention due to their low cost and high oxygen reduction reaction（ORR）activity.Ruthenium（Ru）and Pt are both precious metals,but the price of Ru is less than 1/10of Pt.In addition,Ru has good stability,so it can be applied to fuel cells.In order to reduce the cost of fuel cells and promote the development of fuel cell vehicles,this thesis used Co-based Ru-containing cathode catalysts as research objects to develop Ru-doped Co₃O₄(Ru_xCo_3-xO₄)and carbon-borne Ru Co alloy（Ru Co/C）cathode catalysts for AEMFC and PEMFC respectively.The application of Ru Co/C catalyst in full cells was simulated.The main work is as follows:（1）Ru_xCo_3-xO₄（x=0,0.1,0.15,0.2,0.25,0.3）was prepared and used for ORR catalysis in alkaline medium.As the amount of Ru doping increases,interplanar spacing of the catalysts gradually increase,and the crystal structure remain unchanged.The results of XPS show that the ratio of Co²⁺/Co³⁺and the proportion of O₂^2-/O^-on the catalyst surface increase with the increase of Ru doping.Under the combined influence of these two factors,which have opposite effects on ORR activity,the ORR activity of Ru_xCo_3-xO₄ increases first and then decreases.The ORR activity of Ru_xCo_3-xO₄ is improved compared to Co₃O₄.Ru_0.2Co_2.8O₄ shows the best performance with the onset potential at 0.88 V,the half-wave potential at 0.77 V and the limited current density at 4.41 m A cm^-2.The electron transfer number is 3.58.The Tafel slope is 58.8 m V dec^-1,and it has a higher kinetic reaction rate than commercial platinum carbon（Pt/C）.Thanks to the presence of Ru on the catalyst surface,the stability and methanol resistance of Ru_0.2Co_2.8O₄ are higher than Pt/C.（2）Ru Co/C catalyst was prepared and used to catalyze ORR in acidic medium.With the increase of Ru/Co ratio,the interplanar spacing of the catalyst gradually increases,and all catalysts have hexagonal crystal structure.The ORR activity of catalysts with different Ru/Co ratios is higher than that of Ru/C.Ru Co（2:1）/C shows the best electrochemical performance with the onset potential at 0.77 V,the half-wave potential at 0.59 V and the limited current density at 4.30 m A cm^-2.The electron transfer number is 3.72,indicating that the reaction is mainly a 4-electron reaction process.The Tafel slope of the catalyst is 95.6 m V dec^-1,which has a higher kinetic reaction rate and better stability than Pt/C.（3）Simulate the application of Ru Co/C catalysts in PEMFC based on COMSOL software.The full cell with Ru Co（2:1）/C as cathode catalyst has the highest power density of 422 m W cm^-2.The load of Ru in this fuel cell is 0.12 mg cm^-2,and the power density is higher than the reported power density of Ru₈₅Se₁₅/CA-XC72R as the cathode catalyst.The amount of Ru in the fuel cell is 0.284 g k W^-1,which is higher than the expected value of Pt in automotive fuel cells in 2020(0.125 g k W^-1),but the price of Ru is less than 1/10 of Pt.The higher the cathode gas flow rate,the lower Tafel slope,and the higher electron transfer number,the better the fuel cell performance.The results have guiding significance for catalyst experiments,indicating that the cathode catalyst studied in this paper can effectively reduce the cost of fuel cells,and has important practical value for the development of fuel cell vehicles.