Polyoxometalate-mediated lignin oxidation for efficient enzymatic production of sugars and generation of electricity from lignocellulosic biomass

Abstract

Conversion of lignocellulosic biomass to various renewable fuels, chemicals, materials, and electricity has attracted more and more interest in recent decades to decrease the dependence on fossil resources and reduce net CO₂ emissions. Herein, we have developed an integrated process of biomass pretreatment for enzymatic hydrolysis of cellulose coupled with electricity generation with polyoxometalates (POMs) and ferric ion as electron mediators and proton carriers. The pretreatment is a “charging” process, and the re-oxidation of the POMs is effectively a “discharging” process. The pretreated substrate showed a good enzymatic digestibility (approximately 80% cellulose conversion) within a short incubation period (<24 h). Fe³⁺ was screened as a cheap, effective liquid mediator to transfer electrons to air, which is the terminal electron acceptor in the “discharging” process. The highest output power densities of 10.8 and 12.4 mWcm^-2 were obtained for discharging of reduced H₃PMo₁₂O₄₀ and H₄PMo₁₁VO₄₀, respectively. This power density is 5000–6000 times higher than that of phenol-fueled microbial fuel cells, and 10 times higher than that of a recently reported direct biomass fuel cell with an air cathode covered with Pt catalyst. Moreover, this work also provides a conceptual combination of a direct biomass fuel cell and a redox flow cell, which can be flexibly switched between electricity generation from biomass and stationary energy storage.

Citation

Zhao, Xuebing; Ding, Yi; Du, Bo; Zhu, J. Y.; Liu, Dehua. 2017. Polyoxometalate-mediated lignin oxidation for efficient enzymatic production of sugars and generation of electricity from lignocellulosic biomass. Energy Technology. 5(8): 1179-1185.