Performance And Mechanism Of The Direct Biomass Alkaline Fuel Cell

Glucose and cellulose are abundant, renewable and environmentally friendlybiomass material, which are kind of potential energy. Although they are easy to obtainand convenient to use, current technologies are unavailable for us to directly oxidizethem to obtain energy in the room temperature. Fuel cells using enzymes andmicroorganisms as catalysts are limited by their extremely low power output andrather short durability. Fuel cells using precious metal catalyst are expensive forlarge-scale use.In this paper, we use the constructed one-compartment direct alkaline fuel cell,which use methyl viologen (MV) as electron mediator, nickel foam as the anode andthe carbon cloth containing platinum-carbon catalyst as cathode, to study the effectsof different factors such as glucose, KOH and methyl viologen on the cellperformance. The High-performance liquid chromatography and gaschromatography-mass spectrometry were used to analyze oxidation products ofglucose. The result shows that the maximum power density of the fuel cell gets to0.62mW/cm2in the condition of1M glucose,3M KOH and5mM MV; what’smore, the principal oxidation products are short-chain organic acids indicating deepoxidation of glucose is achieved. In addition, we propose the mechanism of nickelanode and methyl viologen and the reactions of glucose oxidation in the fuel.In the study, we further constructed a alkaline cellulose fuel cell. We studied theeffects of cell anaerobic environment, NaOH concentration and methyl viologenconcentration on the cell performance. Under the optimal condition of1%(w/v)cellulose,5M NaOH and15mM MV, the open circuit voltage is0.55V and themaximum power density of the fuel cell is450mW/m2. High-performance liquidchromatography also detected short-chain aliphatic carboxylic acids in the oxidationproducts. Combined with experimental results and related literature, we propose thatthe cellulose oxidation in our alkaline fuel cell involves the following reactions:mid-chain scission, peeling, enolization/isomerization, β-OH elimination,α-dicarbonyl cleavage and (retro-)aldolization. In addition, using common reed andred algae as fuels, the fuel cell achieved maximum power densities of295mW/m2and 154mW/m2, respectively. These data indicate that by using suitable catalyst andelectrode material, the common carbohydrate biomass can be converted and use moreefficient.