Mechanistic insight into electrocatalytic hydrogenolysis/hydrogenation of aryl ethers over skeletal nickel surface in aqueous phase

Catalytic strategies to complete the cycle of carbon and energy are urgently needed, as they are the key to mitigating the severe challenges of climate change and surface water pollution, while addressing the world's energy needs. To replace conventional petroleum-derived chemical products and energy, utilization of renewable carbon resources in biomass is critical and simple procedures to break down persistent organic pollutants are also needed. This dissertation presents a mild (ambient pressure at 60 ℗ʻC) and effective heterogeneous catalytic strategy that uses skeletal nickel cathodes to electrocatalytically upgrade a variety of aryl ethers and alkyl aryl ethers into simplified, higher energy species by converting them into more valuable smaller aromatic monomers. To successfully breakdown the C-O ether bonds in water insoluble aryl ether substrates, we surveyed different organic co-solvents to achieve the optimal electrocatalytic hydrogenolysis/hydrogenation (ECH) conditions. Importantly, based on the combined observations from rate comparisons, substrate competitions, substituent studies, isotope labeling experiments, and regioselectivity investigations several distinct C-O cleavage mechanisms of these structurally varied aryl ethers were identified. These efforts and insights not only offer guidance to enable rational design of future catalytic approaches, but also reveal the electrocatalyst's ability to achieve the defluorinations of fluorinated aryl ethers bearing sp2 or sp3 C-F bonds.