Integrated Design And Oxygen Reduction Electrocatalytic Performance Of Platinum-Carbon Catalysts

As an efficient energy conversion device,fuel cells have received extensive attention,and their commercial application is an essential part of the sustainable development of hydrogen energy.ORR catalysts,as the core component of fuel cells,determine not only the reaction kinetics and catalytic efficiency of fuel cells,but also their manufacturing costs and service life.Therefore,developing efficient and stable Pt-based electrocatalysts is of great significance for the promotion and application of fuel cells.The primary goal of this thesis is to design high-performance platinum-carbon integrated catalysts.In the integrated construction and synergistic optimization of platinum alloys and modified carbon supports,continuous carbon network supports are continuously improved and upgraded to meet the intrinsic activity of RDE evaluation and mass transport of MEA operation.The main research contents of this thesis are as follows:（1）Pt alloy and graphitic carbon coating are regulated by high-temperature pyrolysis,and a porous PtCuCo@CoNC integrated catalyst is prepared through the integration of the two.In the ORR evaluation,the mass activity of the integrated catalyst at 0.9 V vs.RHE is1.14 A·mg _Pt^-1,and it exhibits superior stability in the long-cycle test of 50,000 cycles,which is attributed to the synergistic catalytic mechanism of multiple sites and the protection of the carbon coating.Theoretical calculations suggest that the synergistic mechanism of Pt Cu Co alloy and Co-N-C sites reduces the two-electron product and enhances the overall efficiency of ORR catalysis.（2）In the previous chapter,the synergistic catalysis of platinum-carbon integrated catalyst improves the intrinsic activity,but its active site utilization may be further improved.The one-dimensional Pt Co@Co NC/NCNT integrated catalyst is constructed by introducing NCNTs support,which improves the dispersion degree and active site utilization of Pt Co nanoparticles in the integrated catalyst.In the ORR test,the initial mass activity of this catalyst at 0.9 V vs.RHE is significantly improved to 1.33 A·mg _Pt^-1.On the basis of synergistic catalysis to enhance the intrinsic activity,the increased active site utilization can further improve the ORR catalytic activity.（3）In the previous two chapters,the construction of platinum-carbon integrated catalyst effectively enhances the ORR catalytic performance.To address the gas diffusion and mass transport issues in the catalytic layer of fuel cells,a multi-dimensional graphitic carbon network is further introduced in the preparation of Pt Co@Co NC/NTG integrated catalyst.The mass activity of the integrated catalyst is 1.52 A·mg _Pt^-1 at 0.9 V vs.RHE,and the mass activity decreases by only 1.3%after 30,000 potential cycles.In the hydrogen-air fuel cell test,the Pt Co@Co NC/NTG integrated catalyst has a current density of 1.50A·cm^-2 at 0.6 V voltage and a maximum power density of 980 m W·cm^-2,indicating improved catalytic performance and mass transport efficiency.Physical field simulations reveal the promotion of gas diffusion and mass transport by porous network channels,resulting in improved ORR catalytic activity and fuel cell operating efficiency.（4）Based on the above research on integrated electrocatalysts,aiming to further develop macro-scale integrated electrodes,self-supporting,large-sized Pt Co@Co NC/PAN and Pt Co@Co NC/CP integrated electrodes are fabricated by electrospinning and carbon paper in-situ growth techniques.At 0.6 V vs.RHE,the Pt Co@Co NC/CP integrated electrode exhibits excellent catalytic activity and optimized mass transport,its current density can reach 192.2 m A·cm^-2,and it can be cycled stably for 2,000 times,far superior to commercial Pt/C.For the Pt Co@Co NC/CP integrated electrode,the integrated construction of the catalytic layer and the gas diffusion layer dramatically improves the compatibility of the two,and promotes the ORR catalytic activity and oxygen diffusion transport.