Search

CO2 catalytic conversion to CO would likely be an important part of CO2 mitigation and utilization. In this work, CuAl2O4 was developed with a spinel structure that acts as an active and stable catalyst for this reaction. Here, the fundamental characteristics of CuAl2O4 catalyst were studied to understand the catalytic mechanism for the Reverse Water Gas Shift reaction. Based on the catalytic mechanism, the CuAl2O4 catalyst was found to have exceptional catalytic activity due to the high dispersion of copper on its surface, and it could have higher catalytic activity by increasing the oxygen vacancies on the surface of the catalyst via alkalinization treatment. By combining with XPS spectra, the relationship between the Raman mode and the oxygen vacancy structure on the CuAl2O4 surface was proved. Through these studies, it was proved that alkalinization treatment can regulate the oxygen vacancies on the surface of the catalyst and thus enhance the catalytic activity. [ABSTRACT FROM AUTHOR]

Nitrogen oxides released from the combustion of fossil fuels are one of the main air pollutants. Selective catalytic reduction technology is the most widely used nitrogen oxide removal technology in the industry. With the development of nanomaterials science, more and more novel nanomaterials are being used as catalysts for the selective reduction of nitrogen oxides. In recent years, metal-organic frameworks (MOFs), with large specific surface areas and abundant acid and metal sites, have been extensively studied in the selective catalytic reduction of nitrogen oxides. This review summarizes recent progress in monometallic MOFs, bimetallic MOFs, and MOF-derived catalysts for the selective catalytic reduction of nitrogen oxides and compares the reaction mechanisms of different catalysts. This article also suggests the advantages and disadvantages of MOF-based catalysts compared with traditional catalysts and points out promising research directions in this field. [ABSTRACT FROM AUTHOR]

Thermochemical processes are considered as a promising technology for sewage sludge management, which could achieve volume reduction, energy and resource recovery, and effective destruction of pathogens. However, there are still many technology limitations and challenges of the thermochemical processes toward industrialization and commercialization. This review first briefly discusses the impact of sewage sludge on environmental sustainability and its current treatment and disposal methods. Typical thermochemical conversion technologies i.e., incineration/combustion, pyrolysis, gasification, and hydrothermal liquefaction for energy and resource recovery from sewage sludge are then comprehensively summarized. Subsequently, the technical challenges of thermochemical conversion of sewage sludge and the solutions that have been and/or are being developed to address the challenges are in-depth analyzed. Meanwhile, the prospects and future directions of the thermochemical technologies are outlined. In addition, the economic analysis and life cycle assessment of thermochemical conversion technologies are evaluated. Finally, the conclusions are put forward. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have been developed into various catalysts with high performance, but employing them for developing highly stable and active nonprecious hydrogen evolution reaction (HER) catalysts still encounters many challenges. To this end, the machine learning (ML) screening of HER catalysts is accelerated by using genetic programming (GP) of symbolic transformers for various typical 2D MA 2 Z 4 materials. The values of the Gibbs free energy of hydrogen adsorption (Δ G H* ) are accurately and rapidly predicted via extreme gradient boosting regression by using only simple GP-processed elemental features, with a low predictive root-mean-square error of 0.14 eV. With the analysis of ML and density functional theory (DFT) methods, it is found that various electronic structural properties of metal atoms and the p-band center of surface atoms play a crucial role in regulating the HER performance. Based on these findings, NbSi 2 N 4 and VSi 2 N 4 are discovered to be active catalysts with thermodynamical and dynamical stability as Δ G H* approaches to zero (-0.041 and 0.024 eV). In addition, DFT calculations reveal that these catalysts also exhibit good deuterium evolution reaction (DER) performance. Overall, a multistep workflow is developed through ML models combined with DFT calculations for efficiently screening the potential HER and DER catalysts from 2D materials with the same crystal prototype, which is believed to have significant contribution to catalyst design and fabrication.

The density and volumetric behavior of three typical n -alkanes (hexane, octane, and decane) influenced by different mole fractions of CO 2 injected in them at temperatures from 303 to 363 K and pressures from 3.8 to 8.67 MPa were investigated by performing molecular dynamics simulations. It is shown that the mass density first increases and then decreases with increasing CO 2 mole fraction. Correspondingly, the system volume only slightly swells at low CO 2 contents while suddenly expanding when the CO 2 mole fraction exceeds a value of ∼60%. The calculations of structural properties and interaction energies indicate that at low CO 2 mole fractions, there are a few CO 2 molecules existing in the gap of alkane molecules, resulting in poor compressibility, while at higher CO 2 concentrations, the CO 2 molecules begin to separate from the CO 2 -saturated alkane phase and form a gas phase, leading to higher compressibility. Therefore, at high CO 2 mole fractions, the system density and volume can more easily be changed by temperature and pressure than that at low CO 2 mole fractions. In addition, since it is harder for alkanes with longer chains to separate from each other, the volume swelling decreases and the density increases with increasing carbon number of n -alkane chains. Finally, we found that the increase in CO 2 mole fraction, temperature, and the decrease in alkane chain length would promote the diffusion of both CO 2 and alkane molecules. However, the influence of pressure on molecular diffusion is very limited except when P = 8.67 MPa and T = 333 K, where CO 2 is in the supercritical state. This work is helpful for understanding the density and volumetric behavior of n -alkane/CO 2 mixtures at a molecular level and provides useful information for guiding carbon sequestration and CO 2 -enhanced oil recovery., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)