Electrochemical refining of long-chain biomass saccharide to high-value d-glucaric acid by preferential 1,4-glycosidic bond cleavage

Hydrogen production coupled with electrochemical refining of long-chain biomass saccharide for high-value d-glucaric acid (GRA) through preferential the 1,4-glycosidic bond cleavage followed by the aldehyde/hydroxyl groups oxidation. [Display omitted] •Biomass saccharide oxidation for glucaric acid coupled with hydrogen production was realized.•Preferential 1,4-glycosidic bond cleavage is followed by the –CHO/ –COOH oxidation.•The –CHO and –CH2OH oxidation in glucose/maltose via NiOOH is spontaneous. Chemicals electrochemical refining coupled with cathode hydrogen production could effectively reduce the overpotential and energy cost. The electrooxidation cleavage of 1,4-glycosidic bond is the urgent problems for high-value d-glucaric acid (GRA) directly from the long-chain biomass saccharide composed of glucose. Hence, we investigated the oxidation path of the maltose over the α-Ni(OH)2 as model electrocatalyst. The results showed that the cleavage potential of maltose 1,4-glycosidic bond is a little higher than that of the aldehyde/hydroxyl groups in glucose, but much lower than that of water. Compared with water oxidation, the aldehyde/hydroxyl groups oxidation could consume the Ni(OH)O intermediate so fast that it cannot accumulate. Operando electrochemical impedance spectroscopy (EIS) showed that the 1,4-glycosidic bond cleavage is not same to the aldehyde/hydroxyl groups oxidation reactions spontaneously, which occurs directly at an initial potential. The morphology of α-Ni(OH)2 would be collapsed and high-priced nickel and metal-oxygen bond would be formed during water oxidation reaction, but which unchanged for glucose and maltose oxidation. In addition, the starch was also used as the long-chain saccharide to study the 1,4-glycosidic bond cleavage and the whole reaction path. This work promotes the development of green electrocatalytic systems to achieve sustainable valorization of biomass saccharide utilization pathways.