Preparation Of Pd/POMs/rGO Composites By Electrodeposition And Its Catalytic Performance For Formic Acid Oxidation

Direct formic acid fuel cell(DFAFCs)can directly convert chemical energy into electrical energy with high energy efficiency and low carbon and nitrogen oxide emissions.So it is a promising clean energy devices for replacement of generator based on combustion.It is very important to develop effective electrocatalysts in the development of fuel cells.At present,palladium catalysts are the most commonly used catalysts for the electrocatalytic oxidation of formic acid.However,the pure palladium catalyst is high cost,poor resistance to CO poisoning.Therefore,how to improve catalytic activity,enhance utilization rate of palladium catalyst and reduce the amount of precious metal is the focus of the present study.Polyoxometalates(POMs)and transition metal substituted Polyoxometalates(TMSPs)have been used as additives for anodic Pd catalysts due to their excellent redox properties,which is aim at enhancing resistance against CO poisoning of Pd catalyst.The transition metal oxide(CoO)surface is rich in oxygen-containing species,so it has strong oxidation ability to CO or other carbon-containing intermediates.At the same time,graphene(rGO)can improve the electron conductivity of the catalyst material and increase the active area when it is used as a catalyst carrier,thereby improving the catalytic activity of the entire catalyst.It is expected that the palladium composites will replace the pure palladium catalyst as the anode catalyst of fuel cell.In this paper,the POMs/rGO and TMSPs/rGO support materials were fabricated by electrochemical-reduction-assisted assembly in order to eletrodeposition Pd and CoO.And three kinds of composite catalysts,Pd/POMs/rGO,Pd/TMSPs/rGO and Pd-CoO/TMSPs/rGO)were prepared.The size,morphology of the composites were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM)and X-ray powder diffraction(XRD).Their constituents and elements valence were analyzed through X-ray photoelectron spectroscopy(XPS),ICP-AES and Raman spectroscopy(Raman).And the electrocatalytic properties for formic acid oxidation are investigated by cyclic voltammetry(CV),chronoamperometry(i-t)CO stripping voltammetry and EIS.The main investigation results are as follows:(1)The as-prepared palladium-based composite catalysts exhibit excellent electrocatalytic activity,stability,electron transporting ability and CO tolerance ability for formic acid oxidation.(2)The electrocatalytic performance of Pd/PW12/rGO is better than that of Pd/SiW12/rGO and Pd/PMo12/rGO catalysts.(3)The electrocatalytic performance of Pd/PWloV2/rGO is better than that of Pd/PW12/rGO,Pd/PW11V/rGO and Pd/PWgV3/rGO catalysts.(4)Introducing CoO to enhance the CO-tolerance ability of Pd-CoO/PW10V2/rGO.