Electricity Storage in Biofuels: Selective Electro-Catalytic Reduction of Levulinic Acid to Valeric Acid Or γ-Valerolactone

For a foreseeable future, the most desirable energy-carriers for transportations remain liquid hydrocarbon fuels, because of their ease, speed and safety of fueling, their efficient distribution network, and their very high energy densities.  Direct storage of electrical energy in high energy-density liquid transportation fuels (electro-biofuels) using electro-catalytic (flow) cell devices shows unique characteristics as compared to other electricity storage devices and provides a promising and sustainable way to store renewable electricity. In this presentation, we reports an effective approach to electricity storage in biofuels via selective electro-catalytic reduction of levulinic acid (LA) to high energy-density valeric acid (VA) or γ-valerolactone (gVL) on a non-precious Pb electrode (99.9%) in a single polymer electrolyte membrane electro-catalytic (flow) cell device, which has demonstrated very high yield of VA (>90%), high Faradaic efficiency (>86%), promising electricity storage efficiency (70.8%) and low electricity consumption (1.5 kWh L^-1_VA). Applied potential and electrolyte pH were found to accurately control the reduction products: lower over-potentials favor the production of gVL, and higher over-potentials facilitate the formation of VA. The effect of molecular structure on electro-catalytic reduction of ketone and aldehyde groups of biomass-derived compounds and our current research on integrated electro-catalytic conversion of LA and formic acid to valeric acid over nanostructured metallic catalysts will also be presented. This “electro-biofuel” technique will have potential to alleviate our long-time addiction to using non-renewable petroleum sources for production of transportation fuels.