Electrochemical CO2 reduction is a prospective strategy to reduce greenhouse gas emissions and produce renewable synthetic fuels. To achieve efficient electrochemical reduction of CO2, near-neutral pH aqueous electrolyte is widely used to provide the highest CO2 solubility and suppress the undesirable hydrogen evolution reaction (HER). In the general electrochemical CO2 reduction system, oxygen evolution reaction (OER) takes place as the counter anodic reaction. However, the overall efficiency of the electrolytic CO2 reduction system can be limited by water oxidation reaction because not only its O2 gas product is not of significant value but also it has slow reaction kinetics, especially near neutral pH with CO2 saturated electrolyte. As an alternative reaction to OER, anodic biomass upgrading coupled with cathodic CO2 reduction can offer noticeable advantages. It is kinetically more favorable while producing value-added chemicals which leads to enhancement in the entire energy efficiency. Indeed, it is attractive pathway of reducing greenhouse gas emissions and fossil-based carbon sources to produce a feedstock from biomass. Among the starting molecules from biomass, 5-hydroxymethylfurfural (HMF) has been estimated as a principal intermediate. Its representative oxidation product, 2,5-furandicarboxylic acid (FDCA) is one of the top value bio-based molecule. Because it can act as a promising building block for bio–polymer synthesis such as polyethylene furandicarboxylate (PEF), which can replace traditional petroleum-based polyethylene terephthalic acid (PET). Herein we electrochemically converted HMF into FDCA catalyzed by nickel oxide nanoparticles (NPs) as an earth abundant 3-d transition metal-based catalyst in CO2-saturated aqueous electrolyte. It is first attempt to produce FDCA without any noble metal catalyst, strong bases, or expensive redox mediators that have been required for electrochemical HMF oxidation. Furthermore, we investigated the mechanism of electrochemical HMF oxidation under CO2-saturated and near-neutral pH mediated by nano-sized nickel oxides. We not only examined the reaction pathway but also conducted electrokinetic and in situ UV-vis spectroscopic analyses. We further proposed a new system, paired electrolysis of CO2 reduction and biomass oxidation, which can produce valuable fuels and chemicals simultaneously by using atmospheric CO2 and biomass derivatives as a carbon source.

Mechanistic investigation on biomass oxidation using nickel oxide nanoparticles in CO2-saturated electrolyte for paired electrolysis

2019 Fall National Meeting

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