The digital economy is an important engine to promote sustainable economic growth. Exploring the mechanism by which the digital economy promotes economic development, industrial upgrading and environmental improvement is an issue worth studying. This paper takes China as an example for study and uses the data of 286 cities from 2011 to 2019. In the empirical analysis, the direction distance function (DDF) and the Global Malmquist-Luenberger (GML) productivity index methods are used to measure the green total factor productivity (GTFP), while Tobit, quantile regression, impulse response function and intermediary effect models are used to study the relationship among digital economy development, industrial structure upgrading and GTFP. The results show that: (1) The digital economy can significantly improve China’s GTFP; however, there are clear regional differences. (2) The higher the GTFP, the greater the promotion effect of the digital economy on the city’s GTFP. (3) From a dynamic long-term perspective, the digital economy has indeed positively promoted China’s GTFP. (4) The upgrading of industrial structures is an intermediary transmission mechanism for the digital economy to promote GTFP. This paper provides a good reference for driving green economic growth and promoting the environment.
For geological sequestration of carbon dioxide (CO2) separated from pulverized coal combustion flue gas, it is necessary to adequately evaluate the potential impacts of flue gas impurities on groundwater aquifers in the case of the CO2 leakage from its storage sites. This study estimated the flue gas impurities to be included in the CO2 stream separated from a CO2 control unit for a different combination of air pollution control devices and different flue gas compositions. Specifically, the levels of acid gases and mercury vapor were estimated for the monoethanolamine (MEA)-based absorption process on the basis of published performance parameters of existing systems. Among the flue gas constituents considered, sulfur dioxide (SO2) is known to have the most adverse impact on MEA absorption. When a flue gas contains 3000 parts per million by volume (ppmv) SO2 and a wet flue gas desulfurization system achieves its 95% removal, approximately 2400 parts per million by weight (ppmw) SO2 could be included in the separated CO2 stream. In addition, the estimated concentration level was reduced to as low as 135 ppmw for the SO2 of less than 10 ppmv in the flue gas entering the MEA unit. Furthermore, heat-stable salt formation could further reduce the SO2 concentration below 40 ppmw in the separated CO2 stream. In this study, it is realized that the formation rates of heat-stable salts in MEA solution are not readily available in the literature and are critical to estimating the levels and compositions of flue gas impurities in sequestered CO2 streams. In addition to SO2, mercury, and other impurities in separated CO2 streams could vary depending on pollutant removal at the power plants and impose potential impacts on groundwater. Such a variation and related process control in the upstream management of carbon separation have implications for groundwater protection at carbon sequestration sites and warrant necessary considerations in overall sequestration planning, engineering, and management.
The goal of global carbon peak and neutrality gives an impetus to the utilization of clean energy (e.g., fuel cell) and carbon dioxide (CO 2 ) at a large scale, where the oxygen reduction reaction (ORR) and CO 2 reduction reaction (CO 2 RR) are the key reactions via the sustainable system, respectively. As a main precursor for fabricating affordable carbon-based electrocatalysts with uniformly dispersed active centers and tailorable performances for ORR and CO 2 RR, metal organic frameworks (MOFs) have captured a surge of interest in recent years. Despite the facilitated development of MOF-derived carbon-based electrocatalysts by many investigations, it is still plagued by high overpotential and unsatisfied life span, which are greatly determined by the efficient and alterable confinement effect on synthesis and performance. In this review, firstly, the confined synthetic strategies (doping engineering, defect engineering, geometric engineering, etc.) of MOF-derived carbon-based electrocatalysts with multi-sized active centers (atom, atomic clusters and nanoparticles (NPs)) are systematically summarized; secondly, the confinement effect on the interaction of ORR and CO 2 RR intermediates, as well as the catalytic durability and activity, was discussed from chemical and physical aspects. In the end, the review discusses the remaining challenges and emerging research topics in the future, including support upgradation and catalyst innovation, high selectivity and effective confinement synthesis, in situ and operando characterization techniques, theoretical investigation, and artificial intelligence (AI) assistant. The new understanding and insights into these aspects will guide the rational confinement concept of MOF-derived carbon-based electrocatalysts for ORR and CO 2 RR with optimized performances in terms of confinement engineering and are believed to be helpful for filling the existing gaps between scientific communities and practical use.Xiaoyu Zhang and Dongping Xue contribute equally to this work.
Storage strata are usually generalized as horizontal when using numerical simulation methods to analyze CO2 geological storage in saline aquifers. However, horizontal strata are not common in nature. Most strata have gradients, because of the effects of geological structure and diagenesis. Based on the actual strata dip angle variation range of two CO2 injection demonstration projects in China, five modeling schemes were designed to investigate the impact of formation dip on CO2 storage amount and space migration of gas‐phase CO2 in reservoir formation. The results show that the total CO2 storage amount is inversely proportional to formation dip, and after injection is halted, storage amounts of upper and lower parts of the same stratum reservoir have a reverse trend. Formation dip has a significant impact on the migration of CO2. The greater the formation dip, the more significant the effect on CO2 migration distance. Given the low porosity and permeability of the Shiqianfeng formation reservoir in the case study, when the stratum dip angle is 16°, at centennial time scale, CO2 migration distance is 47.06% greater than that in the horizontal reservoir. We expect that for storage reservoirs with high porosity and permeability, the influence of formation dip on CO2 migration will be more significant. Because non‐horizontal strata are predominant in deep saline aquifers in nature, regardless of the influence of formation dip, CO2 leakage risks in geological storage will be greatly underestimated. Therefore, in research related to CO2 geological storage, the stratum dip angle must be considered. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd
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