Preparation Of Pitaya Peel-derived Carbon Confined Nickel Based Catalysts And Their Performance Of The Ethanol Oxidation

Currently,in the face of energy crises and environmental issues,developing clean and sustainable energy and equipment has important practical significance.Direct ethanol fuel cells（DEFCs）are considered to be one of the most promising new energy conversion devices due to their high energy density and non pollution advantages.However,its wide commercial application is limited by the slow kinetics of anodic ethanol oxidation.Therefore,in order to solve the kinetic limitations,developing inexpensive and efficient non noble metal based catalysts has become a current research hotspot.In this paper,the pitaya peel（PP）and nickel salt were used as raw material,and the nickel based catalysts were prepared by hydrothermal,impregnation and sol-gel methods.The structures of the catalysts were characterized by scanning electron microscopy,transmission electron microscopy,X-ray diffraction and Raman.The main results are as follows:（1）A carbon material（PPC）was prepared from washed PP through hydrothermal and low-temperature pyrolysis,and then placed in a reactor containing an aqueous solution of nickel chloride.After hydrothermal reaction at a certain temperature for a number of times,it was filtered and washed to obtain Ni Cl₂@PPC Precursor.Under N₂atmosphere,the precursor was placed in a muffle furnace and reacted at constant temperature for 2 h to obtain a nickel based composite.Electrochemical properties indicate that the optimal Ni@PPC-700 composite has excellent activity for ethanol oxidation reactions(132.5 m A cm^-2).At the same time,after 1000 CV cycle stability and 12 h i-t tests,the current density decreased slightly.The excellent performance of the Ni@PPC-700 is mainly attributed to the Ni nanocrystals anchored on the carbon matrix,which avoids the Ni nanocrystals from shedding and aggregating.（2）PPC was dispersed in a beaker containing a mixture of nickel nitrate and ethanol.Then,the beaker was placed in an oven at a constant temperature of 100°C until the solvent dried,and the Ni（NO₃）₂@PPC precursor was prepared.In N₂atmosphere,the precursors were pyrolyzed at constant temperature in muffle furnace for 2 h to prepare nickel-based composite.The electrochemical properties of Ni O@PPC-600indicate that it has excellent activity(231.8 m A cm^-2)for ethanol oxidation.At the same time,after 1000CV cycle stability tests,the retention rate of current density is 90.8%,indicating that Ni O@PPC-600 has good stability.The excellent performance of the Ni O@PPC-600 catalyst is mainly attributed to the fact that its mesoporous structurefacilitates the transport of electrons and electrolyte,the PPC matrix avoids the shedding of active components.And it has moderate lattice defects and graphitization,minimum contact resistance and Tafel slope.（3）PPC was dispersed in the mixed solution of nickel nitrate and cobalt nitrate by the sol-gel method,heated and stirred in a water bath until the formation of gelatin,and then freeze-dried to obtain the precursor,which was pyrolyzed for 2 h in a muffle furnace under N₂atmosphere to obtain composites.Electrochemical properties indicate that the optimal Ni Co@PPC-700 composite has excellent activity for ethanol oxidation reactions(260.9 m A cm^-2).The excellent performance of the Ni Co@PPC-700 is mainly attributed to its moderate lattice defects and degree of graphitization,facilitates to give more active sites.