Recent advances in glycerol valorization via electrooxidation: Catalyst, mechanism and device

Understanding and Suppressing C–C Cleavage during Glycerol Oxidation for C3 Chemical Production

“…Overall, MnSb 2 O 6 is quite selective for C3 products, with >50% selectivity observed across all pH conditions. We note that FA is typically obtained as the major product in strongly acidic (pH 1) or basic (pH 13, 14) media, − and achieving such a high selectivity for C3 products in these conditions has been rarely reported. − The selective production of C3 compounds under strongly acidic or basic conditions may have advantages for practical applications owing to no requirement for buffers and higher electrolysis current generation.…”

“…These drastically different product selectivity results are obtained with oxide catalysts that feature the same metal active site (Mn) and can be attributed to only the different structural (and electronic) features, which highlights the practical outcome of this study. We note that this is the first time such a high selectivity for GLA has been achieved with any non-noble-metal-based electrocatalyst. − We attempted to further increase the FE for GLA by increasing the glycerol concentration to outcompete water oxidation. However, while this results in an increase in the total FE for glycerol oxidation, it is due to an increase in the FEs for GCA and FA, while the FE for GLA remains constant (Figure S6).…”

“…This large supply of glycerol far surpasses its current demand, limiting the price of biodiesel. Thus, the oxidative upgrading of glycerol to various chemicals (Chart ) has been investigated extensively. − In particular, electrochemical approaches are promising since not only does direct electro-oxidation of glycerol promise to be a greener and more sustainable route for the production of these chemicals but electrochemical approaches also have the advantage of pairing glycerol oxidation as the anode reaction with other useful cathode reactions such as hydrogen evolution or CO 2 reduction. − Many chemicals can be obtained from glycerol oxidation, which either maintain the C3 backbone (Chart , blue) or are C2 products resulting from one oxidative C–C cleavage reaction (Chart , purple) or are C1 products resulting from two oxidative C–C cleavage reactions (Chart , green). Generally, formic acid (FA) is found to be the major product from glycerol electrolysis, especially when non-noble-metal-based electrocatalysts are used. ,− While FA is an important industrial chemical that finds use as an animal feed preservative and in the leather and tanning and textiles industries, many of the C2 and C3 products are more valuable (i.e., higher market price) with established or emerging markets. ,− For example, glyceric acid (GLA), one of the C3 products, can be used to produce biobased polymers, surfactants, and skin care products. ,, Thus, there is a need to rationally control the extent of C–C cleavage during glycerol electro-oxidation in order to target specific compounds.…”

Photoassisted Strategy to Promote Glycerol Electrooxidation to Lactic Acid Coupled with Hydrogen Production

“…As shown in Figure 2c, the instead of OER (gray line) by GLY oxidation (purple line) can obviously reduce the electricity consumption of H 2 production from >4 kWh/m 3 H 2 to 2.6 kWh/m 3 H 2 at 300 mA cm −2 and it can be further reduced to 2.1 kWh/m 3 H 2 at 300 mA cm −2 by a photoassisted strategy (300 mW cm −2 ). Considering that the applied light irradiation via a Xe lamp also consumes electricity, 55 in a real application scenario, we can focus sunlight directly using a convex lens, which may minimize electricity consumption for glycerol electrooxidation coupled with hydrogen production.…”

C–C Bond Formation Coupled with C–C Bond Cleavage during Oxidative Upgrading of Glycerol on a Nanoporous BiVO4 Photoanode

“…The glycerol oxidation reaction (GOR) can produce various C3–C1 products (Figure ), nearly all of which are more valuable than glycerol. − Therefore, the production of any of these chemicals would be beneficial if it could be achieved selectively and efficiently. Electro­chemical and photo­electro­chemical GORs are of particular interest, as they can be used as the anode reaction coupled with a cathode reaction that produces fuels (e.g., water reduction to H 2 , CO 2 reduction to C-based fuels, N 2 reduction to NH 3 ) in electro­chemical and photo­electro­chemical fuel production cells. − While water oxidation has typically been used as the anode reaction in these cells, replacing water oxidation with GOR would allow for the simultaneous production of valuable chemicals at the anode and fuels at the cathode within the same cell, increasing the efficacy of the cell.…”