Controllable Preparation And Electrocatalytic Performance Of Pt-based Nano-catalysts

With the goal of "carbon peaking and carbon neutrality ",hydrogen energy is an important energy carrier.Among them,green hydrogen,which is produced by electrolysis of water using renewable energy without producing carbon dioxide,is green,clean and efficient.The production and utilization of green hydrogen can be achieved through regenerative fuel cells(RFC),where the operation efficiency of the system is affected by the performance of electrocatalysts.Both the cathodic hydrogen evolution reaction(HER)process in electrolytic water and the cathodic oxygen reduction reaction(ORR)process in hydrogen fuel cells require Pt-based catalysts,and due to the high price of Pt,how to reduce the Pt loading in the catalysts becomes an urgent problem for RFCs.Therefore,Pt-based catalysts are studied in this paper,focusing on transition metal doping and single-atom catalyst synthesis and preparation methods to improve the utilization of Pt catalysts.The details of the study are as follows:(1)PtCoNi/C nanoparticle catalysts were synthesized by solvent-assisted thermal reduction for oxygen reduction reactions in acidic environments.The PtCoNi/C nanocatalysts had an onset potential of 1.021 V,a half-wave potential of 0.931 V,and a tafel slope of 64.86 mV dec-1.The mass activity(2.50 A/mgPt)and specific activity(5.45 mA/cmPt2)at 0.9 V were 20.8 and 26 times higher than those of commercial Pt/C catalysts,respectively.The calculated number of transferred electrons is close to 4 and the hydrogen peroxide generation rate is below 4%,indicating that the catalyst can produce higher current density.Accelerated degradation test revealed that the mass activity of PtCoNi/C catalyst only decreased by 6.75%after 5000 potentiostatic cycles,still maintaining a high catalytic activity.(2)Single-atom Pt was deposited in Ti vacancies on the surface of monolayer Ti3C2Tx MXene material with defect engineering strategy for hydrogen evolution reaction catalyst in acidic environment.The Pt content in the Pt-Ti3C2Tx catalysts after four potential cycles in electrodeposition was only 0.92 wt%,with overpotentials of 33 mV and 77 mV at 10 mA cm-2 and 100 mA cm-2 respectively.Enhanced etching was used to increase the Ti defects on the Ti3C2Tx carrier surface,to create more anchor site for the Pt atoms,with Pt loading of 1.2 wt%after enhanced etching.The overpotentials at 10 mA cm-2 and 100 mA cm-2 were 31 mV and 67 mV,respectively.The mass activity at-30 mV potential was 3.2 times higher than that of the commercial Pt/C catalyst.And the potential only increased by 3 mV after 42 h of constant current testing.(3)Membrane electrodes(MEA)were further prepared using Pt-Ti3C2Tx as the cathode catalyst for single-cell performance study.The MEA was prepared by hot pressing Pt-Ti3C2Tx catalyst deposited onto carbon paper as cathode diffusion layer with proton exchange membrane and anode diffusion layer sprayed with IrO2 on one side by electrodeposition discharge method,and assembled into a single cell.The single-cell performance test was performed by the constant current method.Among the catalysts with different etching strengths,Pt3.2-Ti3C2Tx showed better catalytic activity with cell potential of 2.075 V at current density of 1 A cm-2.A stability test was carried out for 17 h at current density of 1 A cm-2 with cell potential increase of 10 mV per hour.