Biomass Photoreforming for Hydrogen Production over Hierarchical 3DOM TiO2-Au-CdS

Abstract

Photocatalytic hydrogen production is a promising route to the provision of sustainable and green energy. However, the excess addition of traditional electron donors as the sacrificial agents to consume photogenerated holes greatly reduces the feasibility of this approach for commercialization. Herein, considering the abundant hydroxyl groups in cellulose, the major component of biomass, we adopted glucose (a component unit of cellulose), cellobiose (a structure unit of cellulose) and dissolving pulp (a pretreated cellulose) as electron donors for photocatalytic hydrogen production over a TiO2-Au-CdS material. The well-designed ternary TiO2-Au-CdS possesses a hierarchical three-dimensional ordered macroporous (3DOM) structure, which not only benefits light harvesting but can also facilitate mass diffusion to boost the reaction kinetics. As expected, the fabricated photocatalyst exhibits considerable hydrogen production from glucose (645.1 μmol·h−1·g−1), while the hydrogen production rates gradually decrease with the increased complexity in structure from cellobiose (273.9 μmol·h−1·g−1) to dissolving pulp (79.7 μmol·h−1·g−1). Other gaseous components such as CO and CH4 are also produced, indicating the partial conversion of biomass during the photoreforming process. This work demonstrates the feasibility of sustainable hydrogen production from biomass by photoreforming with a rational photocatalyst design.

Glucose photorefinery for sustainable hydrogen and value-added chemicals coproduction

“…At the same time, the carbon dioxide emitted by the over-oxidation of sacrificial agents during the photocatalytic reaction is not environmentally feasible, making the application of photocatalytic hydrogen production in industrial settings notably difficult. A large number of reducing groups in biomass components, such as hydroxyl groups, can theoretically be used as electron donors for photocatalytic hydrogen production reactions to replace traditional sacrificial agents [9][10][11] . It is believed that through the rational design of bifunctional photocatalysts, realizing the biomass photorefinery process to simultaneously produce sustainable hydrogen and valueadded chemicals is a promising technology for future fuel and chemical production [Figure 1] [12][13][14][15] .…”

Modulating the tunable interfacial charge transfer of Z-scheme TiO2/CdS with Ti–S bonds for enhanced glucose photoreforming

“…[4][5][6] However, the fast carrier recombination in TiO 2 imposes great restrictions on its practical applications. 7 Many strategies have been developed to promote its photocatalytic activity, including cocatalyst modication, metal or nonmetal ion doping, morphology and size modulation, and heterojunction or homojunction construction. Heterojunction construction has proved to be a remarkable way to enhance catalytic activity.…”

“…According to previous reports, the valence band (VB) potential of CdS (around 1.66 eV) is lower than the VB of TiO 2 but is close to its conduction band (about −0.30 eV). 7 This means that photogenerated carrier migration between TiO 2 and CdS can follow the rules of Z-scheme heterojunctions, i.e., the electrons (e − ) in the CB of TiO 2 are more likely to recombine with the holes (h + ) from the VB of CdS. In addition, constructing defects in one semiconductor can achieve further interfacial contact by forming chemical bonds between the two segments.…”