(503f) Membraneless Fuel Cells Modified with Gold Nanoparticles and Laccase for Direct Conversion of Recalcitrant Carbohydrates into Electricity

The need for clean and viable sources of alternative energies has prompted the development of biofuel cells (BFCs), which are characterized by renewability and high power density.In particular, enzymatic BFCs are a special type of fuel cell in which enzymes are used as catalysts to oxidize specific substrates on anodes and reduce O₂ on cathodes.Candidates for substrates include simple sugar like glucose to complex ones such as starch and cellulosic biomass. Since most readily available biomass is in the raw, unprocessed cellulosic form, there is a challenge for BFCs to utilize these complex and recalcitrant substrates.Furthermore, more complex feedstocks such as hydrolysates from lignocellulosic biomass, however, have rarely been used as substrates in BFCs.Typically, some pretreatment or saccharifications are required for these complex feedstocks before they can be used as substrates to generate a high current density.Thus, there is motivation to design, construct and modify BFCs such that they are able to efficiently and effectively utilize various carbohydrate substrates.

In this study, we aim to address problems of using complex substrates by leveraging the catalytic properties of gold nanoparticles (AuNPs) on cathodes and laccase on anodes in a membraneless hybrid BFC. AuNPs are versatile in catalyzing a wide variety of substrates and present a viable alternative to substrate-specific enzyme catalysts that are traditionally used. This is beneficial especially when mixed substrates derived from biomass are used as fuel. We first fabricated and modified cathodes with AuNPs and characterized the effect of the presence of AuNPs (as compared to unmodified electrodes and that modified with bulk gold), AuNP sizes and loadings on the catalytic action of the BFC. Next, the harnessing of stable and useful currents from a variety of carbohydrate substrates was studied: In addition to glucose, other carbohydrates including recalcitrant disaccharides and polysaccharides such as fructose, sucrose and carboxymethylcellulose were also found to successfully generate significant current densities. To further demonstrate the versatility of the BFC, complex feedstocks substrates such as sugarcane bagasse hydrolysate was also shown to deliver a stable current, which was further validated with the lighting up of devices such as light emitting diodes.