Study On ORR Activity And PEMFC Performance Of Ultra-low Pt Catalyst Prepared By Magnetron Sputtering

In recent years,proton exchange membrane fuel cells(PEMFCs)have been applied to many commercial markets,such as portable power supplies,backup power supplies,electric vehicles,etc.Toyota and Honda have been launched commercial fuel cell vehicles.The cost and activity of catalysts will be the critical factor for PEMFC in the current state.Magnetron sputtering is one of the most promising production technology approaches to achieve low Pt and efficient PEMFC due to its advantages of simple and flexible preparation,controllable catalyst size,high production efficiency,low cost,and environmental friendliness.However,there are still some critical issues need to be resolved,such as high activity requirements,low specific surface area and the hydrophilic of sputter Pt.Therefore,in this paper,we systematically study the ORR activity for the dense films and high roughness films of Pt deposited on the glassy carbon of the replaceable disk electrode via magnetron sputtering technology.And the performance of PEMFCs of Pt deposited on the rough texture GDL,grooved GDL with superhydrophobic surface and ultra-thin carbon layer have been also studied.The result shows:(1)The sputtering Pt thin film catalyst has exhibit very excellent ORR activity.The area specific activity(SA)of the dense Pt film at 0.9 V is 782.6?A/cm²_Pt,which is 3.03times that of the commercial Pt/C.However,the electrochemical roughness(R_Pt)of the dense Pt film is only 1.2 cm²_Pt/cm².(2)A high roughness Pt thin film can be obtained by increasing the sputtering pressure and power.The Pt thin film first nucleates in Volmer-Weber growth mode,and then grows into a columnar crystal,forming the high roughness surface.The R_Pt of high roughness Pt thin film reaches 34.56 cm²_Pt/cm² when the Pt loading of 0.12 mg/cm²,which is nearly 30 times higher than that of the dense Pt thin film.And it also exhibits the highest SA of 1205.0?A/cm²_Pt,which is the highest value by far.The discontinuous thin film with the Pt aggregates size of 5?6 nm can be obtained when the ultra-low Pt loading of 0.01 mg/cm²,it has the highest ECSA of 41.5 m²/g _Pt.It also exhibits the highest mass specific activity(MA)of 0.39 A/mg _Pt,which is much higher than the MA(0.24 A/mg _Pt)of commercial Pt/C catalyst prepared by wet chemical method.(3)The optimal loading of sputtering Pt and Nafion are 0.04 mg/cm² and 0.20mg/cm² for porous electrodes with the substrate of GDLs.Compared with commercial GDL(SGL and JNTG),the textured GDL can carry the larger surface area of sputtering Pt due to its higher roughness.The optimal hydrophobic degree of carbon paper is 10wt.%for textured GDL with the more efficient water management.The MEA for porous electrode of textured GDL exhibits the maximum power density of 1.04 W/cm².The mass specific power of Pt deposited on the textured GDL is 26.25 k W/g _Pt,which is higher than that of Pt deposited on the SGL(21.75 k W/g _Pt).In addition,the mass specific power of commercial Pt/C is 24.00 k W/g _Pt with the same Pt loading.(4)The surface contact angle of the grooved GDL with the same groove width and spacing of 25?m is 152.1°.This grooved GDL has super-hydrophobic properties,also has high roughness and permeability.The roughness of the grooved GDL is 3.4 times that of SGL.The gas permeability of the grooved GDL is 3 times that of SGL.The MEA for porous electrode of super-hydrophobic grooved GDL exhibits the maximum power density of 1.47 W/cm².The mass specific power of Pt deposited on the super-hydrophobic grooved GDL is 36.75 k W/g _Pt,which is 2.13 times that of Pt deposited on the SGL and 1.53 times that of commercial Pt/C with the same Pt loading.(5)3 nm Pt particles deposited on ultra-thin carbon layer to prepare the high specific surface area carbon supported Pt catalyst.Compared with commercial Pt/C,sputtered Pt/C has greater ECSA and higher ORR activity.The ECSA of sputtered Pt/C is 79.6m²/g _Pt.The SA of sputtered Pt/C is 346.1?A/cm²_Pt.The maximum power density of the MEA for sputtered Pt/C is 1.87 W/cm²,which is increased by 52%compare with the commercial Pt/C with the same Pt loading under H₂/O₂ test conditions.The mass specific power of sputtered Pt/C is 23.375 k W/g _Pt,which is 1.52 times that of commercial Pt/C catalysts under H₂/O₂ test conditions.The maximum power density of the MEA for sputtered Pt/C is 26.7%higher than that of the commercial Pt/C under H₂/Air test conditions.