Preparation Of Pd/Metal Oxide As Anodic Electrocatalysts For Direct Formate Fuel Cell

With the extravagant consumption of fossil energy and the concomitant environmental issues,cleaning and renewable energy technologies are greatly demanded around the world.Alkaline exchange membrane fuel cell(AEMFC)is promising candidate of renewable energy technologies due to its merit of using non-precious metal materials as cathodic catalysts.Specifically,direct formate fuel cell(DFFC)has attracted extensive attention in the past few years.Pd is considered as a favorable catalyst for formate oxidation reaction(FOR)in DFFC.However,the adsorbed H(Had)is considered as the key intermediate on Pd during FOR,which seriously limited the overall performance of Pd based catalysts.Thus,it is of great significance to rapidly remove Had from Pd catalyst,so as to improve the FOR kinetics.Herein,we prepared Pd loaded transition metal oxides as efficient catalysts to promote the releasing of Had from catalysts,aiming to enhance the FOR performance.(1)Adjusting the metal-support interaction by using modified metal oxide substrate:CeO2 substrate was treated with steam for 2h and further used to load Pd.The obtained Pd/CeO2-2h was used as an efficient catalyst for FOR.Experimental results show that Pd/CeO2-2h possesses rich reactive oxygen species with abundant oxygen vacancies(OVs)at the surface of CeO2.Comparing with the counterpart of Pd/CeO2-untreated,Pd/CeO2-2h exhibited higher FOR performance with lower peak potential and higher stability.Also,Pd/CeO2-2h exhibited lower initial potential for FOR and lower potential of Had desorption.DFT calculations revealed that the enhanced FOR performance is attributed to the promoted*OH adsorption ability derived from oxygen-vacancy-containing CeO2 surface.(2)Hydrogen spillover effect induced by adjusting the morphology Pd:Single atom Pd was deposited on the WO3 substrate to obtain Pd-SA/WO3.Compared with Pd nanoparticle catalyst loaded on WO3 substrate(Pd-NP/WO3),Pd-SA/WO3 has significant lower peak potentials and disappeared shoulder peak corresponded to the Had oxidation,indicating that Had was rapidly desorption from the Pd-SA/WO3.DPV curves showed that the peaks difference of Had desorption were apparently smaller than that observed for Pd-NP/WO3,suggesting fast kinetic of Had oxidation.Mechanism studies show that the enlarged interface and short proton transmission path between Pd-SA and WO3 substrate induce strong hydrogen spillover effect,thus enhancing the desorption of Had from Pd.In summary,Pd/CeO2-2h and Pd-SA/WO3 catalysts were prepared to facilitate the desorption of Had.The mechanism of enhanced FOR performance was thoroughly investigated.This thesis provides useful information for the design and preparation of high performance Pd based catalysts for DFFC.