Understanding the Roles of Electrogenerated Co<sup>3+</sup> and Co<sup>4+</sup> in Selectivity‐Tuned 5‐Hydroxymethylfurfural Oxidation
Xiaohui Deng, Geyang Xu, Yue‐Jiao Zhang, Lei Wang, Jiujun Zhang, Jian‐Feng Li, Xian‐Zhu Fu, Jing‐Li Luo
Abstract
Abstract The Co‐based electrocatalyst is among the most promising candidates for electrochemical oxidation of 5‐hydroxymethylfurfural (HMF). However, the intrinsic active sites and detailed mechanism of this catalyst remains unclear. We combine experimental evidence and a theoretical study to show that electrogenerated Co 3+ and Co 4+ species act as chemical oxidants but with distinct roles in selective HMF oxidation. It is found that Co 3+ is only capable of oxidizing formyl group to produce carboxylate while Co 4+ is required for the initial oxidation of hydroxyl group with significantly faster kinetics. As a result, the product distribution shows explicit dependence on the Co oxidation states and selective production of 5‐hydroxymethyl‐2‐furancarboxylic acid (HMFCA) and 2,5‐furandicarboxylic acid (FDCA) are achieved by tuning the applied potential. This work offers essential mechanistic insight on Co‐catalyzed organic oxidation reactions and might guide the design of more efficient electrocatalysts.