| Fuel cell is one of the effective ways to solve the energy crisis and environmental deterioration because of its high efficiency and no pollution.The most commonly used catalyst in fuel cell is carbon supported platinum or platinum based alloys.However,the commercial development of fuel cell is limited by the high cost and limited reserves of Platinum,thus preparing catalysts with low platinum loading and high performance has been the focus of the researchs.It is well known that the morphology,structure and support materials affect the performance of the catalyst.In recent years,graphene oxide becomes a hot spot because of its high surface area,tunable surface functional groups and good conductivity.In addition,Pt nanocrystals have a good application prospect in the electrochemical reaction of methanol oxidation and formic acid oxidation,because they have many advantages such as tunable physical and chemical properties,special morphology,high surface area and good dispersion.Many studies have shown that the high index surface catalyst has better catalytic activity and stability compared with the low index crystal surface,and the square-wave method is an effective way to obtain high index surface platinum nanocatalyst.In this paper,carbon fiber paper(CFP)wrapped with reduced graphene oxide(rGO)film is prepared to support Pt nanocrystals(NCs)deposited through square-wave potential method.It is found that Pt NCs become smaller and more regular with the increases of rGO reduction degree.The main research work is as follows:GO aqueous solution is firstly directly added onto the surface of carbon fiber paper(CFP)and dried to form a film in the space between the carbon fibers,anneal reduction method is employed to obtain rGO/CFP;following that,Pt NCs are deposited on the rGO/CFP by square-wave potential method.SEM results indicated that the places between the carbon fiber were almost coated by rGO film.The results of XPS,FTIR and Raman indicated that rGO was highly reduced under the condition of 800 ℃ and hydrogen atmosphere,while the C-O bond was almost disappeared,and the oxygen content was only about 6.1 wt%.It is found that the irregular Pt NCs-62 nm are electrodeposited on low reduced rGO while the uniform Pt NCs～20 nm with concave nanocubes(CNC)structure are electrodeposited on high reduced rGO.The obtainted CNC Pt-HrGO/CFP present a high electrochemically active surface area(121.7 m2 g-1,),as well as enhanced electrooxidation activity of methanol(499.2 mA mg-1)and formic acid(949.8 mA mg-1).The results show that the CNC Pt-rGO/CFP composite electrode has higher electrocatalytic performance and stability,which can be attributed to the small size and unique CNC structures bounded by high index facets of Pt NCs.PEMFC test is used to characterize the performance of Pt-rGO/CFP composite electrode,and the maximum power density is 1855.3 mW mg-1.Pt-rGO/CFP electrode prepared by sputtering method is also used in this paper,and the effect of square-wave on the morphology and catalytic performance of the Pt-rGO/CFP electrode is investigated.This research not only provide an attractive perspective on the convenient preparation of low-cost gas diffusion electrode(GDE),but also to provide some guidance and reference for the development of low platinum loading and high performance GDE in fuel cells. |
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