Enzymatic biomass hydrolysis assisted photocatalytic H2 production from water employing porous carbon doped brookite/anatase heterophase titania photocatalyst

Abstract

Solar reforming cellulosic biomass into hydrogen is a promising approach for sustainable biomass waste utilization and renewable energy development. To overcome the challenge of depolymerization of rigid cellulose in mild conditions, a strategy that combines enzymatic hydrolysis of cellulose with photocatalytic H2 production from water under mild conditions has been proposed. Specifically, porous carbon doped brookite/anatase heterophase titania as a representative photocatalyst has been synthesized by an easy self-assembly and growth approach. The typical characteristics of porous structure, carbon doping as well as heterojunction formation of the prepared photocatalyst result from the self−assembled crystallization and low temperature annealing processes, and the special structural effects on the improved photochemical behavior were investigated through a series of characterizations. The synthesized TiO2 annealed at 200 °C (Meso-TiO2-200) presents remarkable H2 production performance even without cocatalyst loading under UV light irradiation. Furthermore, the enzymatic hydrolysis of cellulose and raw biomass materials has been optimized in terms of reaction temperature, solution pH and types of enzyme to obtain higher yields of glucose. Lastly, the H2 production from water employing with the Meso-TiO2-200 photocatalyst and enzymatic depolymerized products as sacrificial agents has been quantitively evaluated. The H2 yields are about 56 μmol/g.cat (5 h) and 2965 μmol/g.cat (5 h) at pH 7 for Meso−TiO2−200 without or with 1.0 wt% Pt cocatalyst loading, significantly higher than that of the commercial P25 sample. Under the optimized condition, the apparent quantum efficiency under 365 ± 10 nm irradiation was about 1.95%, and the mechanism for the improved H2 production has been proposed.