Phosphomolybdic Acid as a Catalyst for Oxidative Valorization of Biomass and Its Application as an Alternative Electron Source
Hyeonmyeong Oh, Yuri Choi, Changhwan Shin, Trang Vu Thien Nguyen, Yujin Han, Hyunwoo Kim, Yong Hwan Kim, Jae‐Won Lee, Ji‐Wook Jang, Jungki Ryu
Abstract
Power- and solar-to-chemical energy conversion has been spotlighted as a promising technology for the efficient use of renewable energy resources. In principle, various chemicals can be sustainably produced through (photo)electrochemical reduction using water as a cheap and clean electron source. However, oxidation of water is a challenging task that results in low energy efficiency and reliability issues for the practical application of power- and solar-to-chemical energy conversion. Here, we show that various biomasses including lignin can be used as alternative electron sources. Electrons can be readily extracted from biomass using phosphomolybdic acid as a catalyst for oxidative depolymerization of biomass and an electron mediator at a much lower potential (0.95 V vs. reversible hydrogen electrode) than water using the best-performing but expensive catalysts (1.5-1.6 V). In particular, value-added chemicals such as CO and vanillin are produced as byproducts upon oxidative depolymerization of lignin. As a result, this approach allows efficient (photo)electrochemical production of hydrogen with a Faradaic efficiency close to unity at acidic pHs and brings additional economic benefits from byproducts.