This review concisely reports the photoreduction mechanism of CO₂, construction, application, and upgrade strategies for Z-scheme heterostructures.

Ethanol, as one of the important bulk chemicals, is widely used in modern society. It can be produced by fermentation of sugar, petroleum refining, or conversion of syngas (CO/H₂). Among these approaches, conversion of syngas to ethanol (STE) is the most environmentally friendly and economical process. Although considerable progress has been made in STE conversion, control of CO activation and C–C growth remains a great challenge. This review highlights recent advances in the routes and catalysts employed in STE technology. The catalyst designs and pathway designs are summarized and analysed for the direct and indirect STE routes, respectively. In the direct STE routes (i.e., one-step synthesis of ethanol from syngas), modified catalysts of methanol synthesis, modified catalysts of Fischer–Tropsch synthesis, Mo-based catalysts, noble metal catalysts and multifunctional catalysts are systematically reviewed based on their catalyst designs. Further, in the indirect STE routes (i.e., multi-step processes for ethanol synthesis from syngas via methanol/dimethyl ether as intermediates), carbonylation of methanol/dimethyl ether followed by hydrogenation, and coupling of methanol with CO to form dimethyl oxalate followed by hydrogenation, are outlined according to their pathway designs. The goal of this review is to provide a comprehensive perspective on STE technology and inspire the invention of new catalysts and pathway designs in the near future.

Thermal decompositions of three components of biomass (cellulose, hemicellulose and lignin) were studied using nonisothermal thermogravimetric analysis (TGA) under both oxidative and inert atmospheres at a heating rate of 10 K min(-1). The multi-Gaussian-distributed activation energy model (DAEM)-reaction model was first developed to describe thermal decomposition behaviors of three components. Results showed that the presence of CO₂ enhanced the thermal decompositions of three components in high temperature range, but made little difference in low temperature range. Decomposition behaviors under CO₂ were analyzed by the two-stage reaction mechanism corresponding to the pyrolysis process of original materials and the gasification process of char. During gasification stage, CO₂ was reduced to CO, which provided a possibility of a reduction in greenhouse gas emissions. In addition, more CO was produced, and therefore the thermal value of gas was improved. The findings imply that CO₂ gasification technology of biomass has great research significance.

This work deals with the pyrolysis kinetics of cellulose, hemicellulose and lignin. Experiments were carried out in a thermogravimetric analyzer (TGA Q5000) in the inert atmosphere of nitrogen at a heating rate of 10 K min⁻¹. The single Gaussian distributed activation energy model (DAEM) was utilized to study the pyrolysis kinetics. Kinetic parameters such as the pre-exponential factor (k₀), mean activation energy (E₀) and standard variance (σ) were computed by a pattern search algorithm. It was found that the calculated kinetic parameters using the single Gaussian-DAEM-reaction model could reproduce the differential thermogravimetric (DTG) curves of cellulose very well. However, there existed obvious deviations in the whole range of temperatures between the calculated and experimental data for hemicellulose and lignin. In order to describe the thermal decompositions of hemicellulose and lignin more accurately, a novel double Gaussian-DAEM-reaction model consisting of two parallel partial reactions was developed to describe the pyrolysis processes. Calculated results of the fitting procedure using the double Gaussian-DAEM-reaction model showed good agreement with experimental DTG data of hemicellulose and lignin.

Thermogravimetric experiments of two different industrial sludge samples were carried out with non-isothermal temperature programs. The results indicated that the pyrolysis process contains three obvious stages and the main decomposition reaction occurred in the range of 200-600°C. The distributed activation energy model (DAEM) was also proposed describing equally well the pyrolysis behavior of the samples. The calculated activation energy was ranged from 170 to 593kJ/mol and 125 to 756kJ/mol for SLYG (sludge sample from chemical fiber factory) and SQD (sludge sample from woody industry), respectively. The reliability of this model not only provided good fit for all experiments, but also allowed accurate extrapolations to relative higher heating rates. Besides, the FTIR measurement was also used to further understand the relationship between pyrolysis behavior and chemical structures for industrial sludge.