聚多巴胺包覆银衍生氧还原电催化剂的合成

Preparation of Ag@polydopamine derived oxygen reduction electrocatalyst

以聚多巴胺(PDA)为载体,利用多巴胺的还原性在碱性条件下还原硝酸银,再经过高温热解,使聚多巴胺碳化,合成了Ag@C-PDA催化剂.这种催化材料在氧还原反应(ORR)相关的测试当中有较好的表现,在0.1 mol·L^(-1)的KOH电解质中起始电位和半波电位分别为0.879和0.731 V(νs.RHE),在电势为0.4 V时,其动力学极限电流密度可达到4.81 mA·cm^(-2).经过20000 s的i-t循环后,Ag@C-PDA催化剂的电流衰减仅为3%,表现出了优于商业Pt/C的稳定性.Ag@C-PDA良好的ORR电化学活性源于本身具有较强导电性的Ag纳米粒子均匀分散以及碳材料较高的石墨化程度.

With the acceleration of the process of industrialization,people's demand for global energy has also begun to increase sharply.Although fossil fuels have brought huge economic benefits to mankind and promoted the process of social industrialization,the consumption of fossil fuels has brought a series of environmental degradation and energy depletion problems.On the other hand,these problems bring new challenges.In order to solve these problems,the top priority is the use of renewable energy(wind energy,solar energy,geothermal energy,tidal energy,hydrogen energy and so on).Therefore,people begin to focus on the development of new energy storage equipment.Proton exchange membrane fuel cell(PEMFC)is a kind of safe and environmentally friendly electrochemical energy conversion device with great prospects.It has the advantages of eco-friendliness,high efficiency and high energy density,and can directly convert chemical energy into electrical energy.Among them,oxygen reduction(ORR)catalyst can play a key role in the research of this equipment.Platinum-based catalysts are used as commercial catalysts due to their good ORR catalytic activity.However,the high cost of precious metal platinum and scarce resources limit its application.Therefore,it is necessary to find cheap and easy-to-obtain electrocatalysts with high-efficiency ORR activity.Finding a suitable catalyst plays an important role in the development of PEMFC.In this paper,polydopamine(PDA)was selected as the carbon source,and silver nanoparticles were encapsulated by the PDA derived carbon layer to generate a carbon-precious metal composite electrocatalyst.In the formation process,dopamine reduces silver nitrate to silver nanoparticles under alkaline conditions owing to its reducibility and the oxidized product PDA can be considered as a carrier.After high-temperature pyrolysis,the polydopamine is carbonized and wrapped in the outer layer of silver nanoparticles to synthesize Ag@carbonized polydopamine(Ag@C-PDA)catalyst.This catalytic material has a good performance in ORR related tests.The initial potential and half-wave potential in 0.1 mol·L^(-1)KOH electrolyte are 0.879 and 0.731 V,respectively(compared to the standard reversible hydrogen electrode),and at the potential of 0.4 V,the kinetic limiting current density reaches 4.81 mA·cm^(-2),close to that of the commercial Pt/C.After an i-t cycle of 20000 s,the current decay of the Ag@C-PDA catalyst is only 3%,showing its better stability than commercial Pt/C(19.1%).According to the research analysis,the good ORR electrochemical activity of Ag@C-PDA comes from the uniform dispersion of Ag nanoparticles with strong conductivity,the high degree of graphitization of carbon materials and the increased oxygen vacancy content.Therefore,Ag@C-PDA can be considered as a potential eletrocatalyst for wide application in PEMFC field.