Cellobiose hydrolysis and decomposition by electrochemical generation of acid and hydroxyl radicals.

This paper addresses the hydrolysis of cellobiose to glucose and its further decomposition with electrochemically generated acid (H(+)) on a platinum electrode, and with electrochemically generated hydroxyl radicals (OH(·)) on boron-doped diamond (BDD). The results are compared with the hydrolysis promoted by conventional acid (H(2)SO(4)) and OH(·) (from Fenton's reaction) and supported by product analysis by using online HPLC (for soluble products) and online electrochemical mass spectrometry (for CO(2)). Cellobiose hydrolysis follows a first-order reaction, which obeys Arrhenius' law over the temperature range from 25-80 °C with different activation energies for the acid- and radical-promoted reaction, that is, approximately 118±8 and 55±1 kJ mol(-1), respectively. The high local acidity with electrochemically generated H(+) on the Pt electrode increases the rate of glucose formation, however, the active electrode (PtO(x)) interacts with glucose and decomposes it further to smaller organic acids. In addition, O(2) formed during the oxygen evolution reaction (OER) lowers the selectivity of glucose by forming side-products. OH(·) generated on a BDD electrode first hydrolyzes the cellobiose to glucose, but rapidly attacks the aldehyde on glucose, which is further decomposed to smaller aldoses and finally formaldehyde, which is subsequently oxidized electrochemically to formic acid.