Rational Design of S‐Scheme Heterojunction toward Efficient Photocatalytic Cellulose Reforming for H₂ and Formic Acid in Pure Water

Abstract

Photocatalytic cellulose reforming usually requires harsh conditions due to its sluggish kinetics. Here, a hollow structural S-scheme heterojunction of ZnSe and oxygen vacancy enriched TiO₂ , namely, h-ZnSe/Pt@TiO₂ , is designed and fabricated, with which the photocatalytic reforming of cellulose for H₂ and formic acid is realized in pure water. H₂ and formic acid productivity of 1858 and 372 µmol g^-1 h^-1 and a steady H₂ evolution for 300 h are achieved with α-cellulose. Comparable photocatalytic activity can also be achieved using various cellulose sources. It is experimentally proven that the photogenerated charge transfer follows an S-scheme mechanism, which not only promotes the charge separation but also preserves the higher reductive and oxidative abilities of the ZnSe and TiO₂ , respectively. Furthermore, the polyhydroxy species produced during cellulose degradation are favored to adsorb on the oxygen vacancy enriched TiO₂ surface, which promotes the photocatalytic reforming process and is accounted to the preservation of formic acid as the major solution-phase product. In addition, sequential reactions of oxidation of aldehydes and elimination of formic acid of the cellulose degradation process are revealed. This work provides a photocatalytic strategy to sustainably produce hydrogen and value-added chemicals from biomass under the most environmentally benign condition, i.e., pure water.