Active Hydroxyl-Mediated Preferential Cleavage of Carbon-Carbon Bonds in Electrocatalytic Glycerol Oxidation.

Electrocatalytic glycerol oxidation reaction (GOR) to produce high-value formic acid (FA) is hindered by high formation potential of active species and sluggish C-C bond cleavage kinetics. Herein, Ni single-atom (Ni) and Co single-atom (Co) dual sites anchored on nitrogen-doped carbon nanotubes embedded with NiCo alloy (NiCo@NiCo-NCNTs) are constructed for electrochemical GOR. Remarkably, it can reach 10 mA cm at a low potential of 1.15 V versus the reversible hydrogen electrode (vs. RHE) and realize a high formate selectivity of 93.27 % even at high glycerol conversion of 98.81 % at 1.45 V vs. RHE. The GOR mechanism and pathway are systematically elucidated via experimental analyses and theoretical calculations. It is revealed that the active hydroxyl (*OH) can be produced during the GOR. The Ni, Co, and NiCo synergistically optimizes the electronic structure of Co active sites, reducing the energy barriers of *OH-mediated cleavage of C-C bonds and dehydrogenation of C intermediates. This decreases the number of reaction intermediates and reaction steps of GOR-to-FA, thus increasing the formate production efficiency. After coupling GOR with hydrogen evolution reaction in a membrane electrode assembly cell, 14.26 g of formate and 23.10 L of H are produced at 100 mA cm for 108 h.