Preparation Of Cobalt-based Oxide Nanocatalysts And Their Application In Direct Glucose Fuel Cells

With the increasing demand for energy and the gradual depletion of fossil fuels,the development of clean and renewable energy has become an inevitable issue in each country.Glucose is the most widely distributed monosaccharide in nature which is a new energy source of great concern with many advantages,such as renewable,easy-storage,nontoxic,and low-cost.However,the process of obtaining electricity from glucose has encountered bottlenecks such as expensive catalyst and low efficiency of utilization.Among many non-noble metal catalysts,heteropoly acid and spinel catalysts have attracted much attention in recent years because of their low cost and excellent performance.However,there are no reports about their application in the electrochemical oxidation of glucose,and there is no relevant mechanism research.In this paper,we modified activated carbon anode with three different heteropoly acids（phosphotungstic acid,silicotungstic acid and phosphometanic acid）and their performances were characterized by various electrochemical techniques.Our results showed that phosphotungstic acid had the ability to catalyze the oxidation of glucose.Then cobalt,ferric and nickel were respectively added into the phosphotungstic acid solution to prepare Lewis acid catalysts.The results of LSV,EIS and Tafel show that anode performance of the fuel cell equipped with Co-PW₁₂ was the best,and the maximum power density of the fuel cell equipped with the anode is 35.78 W m^-2 at room temperature,which is 1.64 times that of the control(21.88 W m^-2)without Co-PW₁₂.The maximum power density can reach 48.37 W m^-2 at 50°C,even higher than most of the published values.The high electrocatalytic activity of the Co-PW₁₂ towards glucose oxidation is ascribed to the synergetic effect between two redox couples,Co²⁺/Co³⁺and[（PW）₁₂]_Ox/[（PW）₁₂]_Re,which promote glucose oxidation rate and accelerate the transfer of electrons to external circuits.The[（PW）₁₂]_Ox may be good at capturing electrons released from glucose.This procedure can be accelerated by redox couple Co²⁺/Co³⁺..In addition,the immobilization of Co-PW₁₂ can benefit the stability of the catalysts,extends their life time,reduces the cost,and decreases avoid adverse environmental effects.Then,the FeCo₂O₄ catalyst particles were prepared by a facile solvothermal method.The results of XRD,XPS and SEM showed that the prepared catalysts were porous FeCo₂O₄ with spinel structure.Perfomance of activated carbon anode was dramatically enhanced by modification with FeCo₂O₄ catalyst,and the optimum content was 2%of activated carbon.The maximum power density of the fuel cell equipped with the FeCo₂O₄ modified anode at room temperature is 35.91 W m^-2,which is 1.51 times the performance of the blank anode.The excellent electrocatalytic performance of FeCo₂O₄ catalyst is supposedly attribute to the two redox couples,Fe²⁺/Fe³⁺和Co²⁺/Co³⁺,,which can significantly accelerate the electron transfer between glucose molecules and current collector..In this paper,we developed two low-cost and high-efficiency catalysts for electrochemical oxidation of glucose in alkaline environment.The mechanisms for glucose oxidation catalyzed by these two types of catalysts in alkaline environment were primarily studied,which provides theoretical support for the further improvement and application of direct glucose fuel cells.