Electro-catalytic water-to-oxygenates conversion: redox-mediated versus direct oxygen transfer

Abstract

Electro-catalytic oxygenation of hydrocarbons with high selectivity has attracted much attention for its advantages of sustainable and controllable production of oxygenated compounds with reduced greenhouse gas emissions. Especially when utilizing water as the oxygen source, by constructing the water-to-oxygenates conversion system at the anode, the environment and/or energy costs of producing oxygenated compounds and hydrogen energy can be significantly reduced. There is an extensive consensus that the generation and transformation of oxygen species are among the decisive factors determining the overall efficiency of oxygenation reactions. Thus, it’s necessary to elucidate the oxygen transfer process to suggest more efficient strategies for electro-catalytic oxygenation. Herein, we introduce the oxygen transfer routes through redox-mediated pathways or direct oxygen transfer methods. Especially for the scarcely investigated direct oxygen transfer at the anode, we aim to detail the strategies of catalyst design targeting the efficient oxygen transfer process including activation of organic substrate, generation/adsorption of oxygen species, and transformation of oxygen species for oxygenated compounds. Based on these introduced examples, the significance of balancing the generation and transformation of oxygen species, tuning the states of organic substrates and intermediates, accelerating electron transfer for organic activation et al. for direct oxygen transfer has been elucidated. Moreover, the greener organic synthesis routes through heteroatom transfer and molecular fragment transfer have been expected beyond oxygen transfer.