Combining heterogeneous photocatalysis and enzymatic catalysis via membrane: Conversion of biomass for H₂ production from water

Solar reforming cellulosic biomass into hydrogen is an attractive research topic for sustainable biomass waste utilization and renewable energy development. To exert the advantages of enzymatic catalysis and heterogeneous photocatalysis, a glass fiber membrane integrated process that combines enzymatic hydrolysis of cellulose with sacrificial photocatalytic H₂ production from water under mild condition has been proposed as an example of integrating enzymatic catalysis and heterogeneous photocatalysis. Specifically, a low−cost Cu_0.5Ni_0.5−TiO₂ photocatalyst has been developed with presenting remarkable H₂ production performance even comparable with Pt−TiO₂ under UV light irradiation. The synergistic effect of Cu and Ni co−deposition onto TiO₂ has been found to improve the photocatalytic H₂ production. The condition for enzymatic hydrolysis of cellulose to generate glucose has been optimized in terms of reaction temperature, solution pH, types of cellulase and inorganic ions in order to obtain higher yields of glucose. To integrate the enzymatic catalysis and photocatalysis together, the glass fiber membrane with superior glucose penetration capability has been screened out. Lastly, the coupling of photocatalytic H₂ production from water based on the Cu_0.5Ni_0.5 −TiO₂ photocatalyst and enzymatic hydrolysis of cellulose has been quantitively evaluated in both mixed and membrane−separation systems. The membrane−separation system can avoid the depletion of cellulase activity induced by photocatalytic oxidation, and thus presents higher H₂ production efficiencies with apparent quantum efficiency of 3.07 % at 365 ± 10 nm irradiation in initial 5 h. This work demonstrates that inorganic membrane integrated enzymatic catalysis and photocatalysis can be a powerful tool for different potential applications.