Photocatalytic conversion of CO to fuels with water by B-doped graphene/g-C3N4 heterostructure

Abstract

Photocatalytic reduction of carbon monoxide (CO) is a promising route to the production of high-value chemicals and fuels, as a supplement to high energy-input Fischer-Tropsch synthesis (FTS) and a key step in direct photo/electro-reduction CO2 to multi-carbon products. However, many current research efforts for high-efficiency FTS/CO2 reduction mainly focus on the metal-based catalysts, while metal-free and solar-driven photocatalysts are rarely explored. Here, by means of Lewis acid sites, a metal-free composite photocatalyst for CO reduction, namely boron (B) doped-graphene/g-C3N4 heterostructure, is proposed. First-principles calculations show that the dopants (B) as catalytic sites can effectively capture and activate CO molecules and reduce CO to CH3OH and CH4 in different doping content. It is worth noting that C2 products, i.e., C2H5OH, can be produced with low free energy barriers on para-doped graphene/g-C3N4. Meanwhile, the competitive hydrogen evolution reaction (HER) can be greatly suppressed, leading to the high selectivity of CO reduction. Moreover, the formation of a built-in electric field in heterostructure enhances the separation of photogenerated electrons and holes, which further accelerates the transmission of photogenerated electrons to the catalytic sites and improves the reaction efficiency. Overall, this work not only proposes a new strategy from a new perspective to solve problems of high energy consumption and low selectivity of FTS, but also provides a tandem strategy to solve problems of CO2 to multi-carbon products.