Electrogenerated alkaline hydrogen peroxide for rice straw pretreatment to enhance enzymatic hydrolysis.

In this work, alkaline hydrogen peroxide (AHP) solution with 1 wt% H2O2 was electrogenerated by oxygen reduction with a current efficiency of 75.2% in a home-made gas diffusion electrode-based electrochemical cell and used for rice straw pretreatment (0.1 g H2O2/g rice straw, 10% (w/v) biomass loading, 55 °C, 2 h). Results showed that the AHP pretreatment removed 97.56% of the initial lignin, 85.75% of the initial hemicellulose, and only 0.56% of the initial cellulose, and the specific surface area and porosity of the AHP pretreated rice straw (AHP-RS) were greatly increased. Saccharification results showed that after 48 h of enzymatic hydrolysis AHP-RS achieved a 3.2-fold increase in reducing sugar concentration compared to the untreated rice straw (5.81 and 1.81 g L-1), highlighting the potential use of this AHP solution for lignocellulose pretreatment.

Effect of the components' interface on the synthesis of methanol over Cu/ZnO from CO2/H2: a microkinetic analysis based on DFT + U calculations.

The elucidation of chemical reactions occurring on composite systems (e.g., copper (Cu)/zincite (ZnO)) from first principles is a challenging task because of their very large sizes and complicated equilibrium geometries. By combining the density functional theory plus U (DFT + U) method with microkinetic modeling, the present study has investigated the role of the phase boundary in CO2 hydrogenation to methanol over Cu/ZnO. The absence of hydrogenation locations created by the interface between the two catalyst components was revealed based on the calculated turnover frequency under realistic conditions, in which the importance of interfacial copper to provide spillover hydrogen for remote Cu(111) sites was stressed. Coupled with the fact that methanol production on the binary catalyst was recently believed to predominantly involve the bulk metallic surface, the spillover of interface hydrogen atoms onto Cu(111) facets facilitates the production process. The cooperative influence of the two different kinds of copper sites can be rationalized applying the Brönsted-Evans-Polanyi (BEP) relationship and allows us to find that the catalytic activity of ZnO-supported Cu catalysts is of volcano type with decrease in the particle size. Our results here may have useful implications in the future design of new Cu/ZnO-based materials for CO2 transformation to methanol.