The steel industry is a major source of CO2 emissions, and thus, the mitigation of carbon emissions is the most pressing challenge in this sector. In this paper, international environmental governance in the steel industry is reviewed, and the current state of development of low-carbon technologies is discussed. Additionally, low-carbon pathways for the steel industry at the current time are proposed, emphasizing prevention and treatment strategies. Furthermore, the prospects of low-carbon technologies are explored from the perspective of transitioning the energy structure to a “carbon–electricity–hydrogen” relationship. Overall, steel enterprises should adopt hydrogen-rich metallurgical technologies that are compatible with current needs and process flows in the short term, based on the carbon substitution with hydrogen (prevention) and the CCU (CO2 capture and utilization) concepts (treatment). Additionally, the capture and utilization of CO2 for steelmaking, which can assist in achieving short-term emission reduction targets but is not a long-term solution, is discussed. In conclusion, in the long term, the carbon metallurgical process should be gradually supplanted by a hydrogen–electric synergistic approach, thus transforming the energy structure of existing steelmaking processes and attaining near-zero carbon emission steelmaking technology.
A series of carbon nitride (CN) materials represented by graphitic carbon nitride (g-C3N4) have been widely used in bioimaging, biosensing, and other fields in recent years due to their nontoxicity, low cost, and high luminescent quantum efficiency. What is more attractive is that the luminescent properties such as wavelength and intensity can be regulated by controlling the structure at the molecular level. Hence, it is time to summarize the related research on CN structural evolution and make a prospect on future developments. In this review, we first summarize the research history and multiple structural evolution of CN. Then, the progress of improving the luminescence performance of CN through structural evolution was discussed. Significantly, the relationship between CN structure evolution and energy conversion in the forms of photoluminescence, chemiluminescence, and electrochemiluminescence was reviewed. Finally, key challenges and opportunities such as nanoscale dispersion strategy, luminous efficiency improving methods, standardization evaluation, and macroscopic preparation of CN are highlighted.
Understanding the adsorption interactions between carbon materials and sulfur compounds has far-reaching impacts, in addition to their well-known important role in energy storage and conversion, such as lithium-ion batteries. In this paper, properties of intrinsic B or Si single-atom doped, and B–Si codoped graphene (GR) and graphdiyne (GDY) were investigated by using density functional theory-based calculations, in which the optimal doping configurations were explored for potential applications in adsorbing sulfur compounds. Results showed that both B or Si single-atom doping and B–Si codoping could substantially enhance the electron transport properties of GR and GDY, improving their surface activity. Notably, B and Si atoms displayed synergistic effects for the codoped configurations, where B–Si codoped GR/GDY exhibited much better performance in the adsorption of sulfur-containing chemicals than single-atom doped systems. In addition, results demonstrated that, after B–Si codoping, the adsorption energy and charge transfer amounts of GDY with sulfur compounds were much larger than those of GR, indicating that B–Si codoped GDY might be a favorable material for more effectively interacting with sulfur reagents.
The excessive use of nonrenewable energy has brought about serious greenhouse effect. Converting CO2 into high-value-added chemicals is undoubtedly the best choice to solve energy problems. Due to the excellent cost-effectiveness and dramatic catalytic performance, nickel-based catalysts have been considered as the most promising candidates for the electrocatalytic CO2 reduction reaction (eCO2RR). In this work, the electrocatalytic reduction mechanism of CO2 over Ni-based materials is reviewed. The strategies to improve the eCO2RR performance are emphasized. Moreover, the research on Ni-based materials for syngas generation is briefly summarized. Finally, the prospects of nickel-based materials in the eCO2RR are provided with the hope of improving transition-metal-based electrocatalysts for eCO2RR in the future.
The artificial photosynthesis technology has been recognized as a promising solution for CO2 utilization. Photothermal catalysis has been proposed as a novel strategy to promote the efficiency of artificial photosynthesis by coupling both photochemistry and thermochemistry. However, strategies for maximizing the use of solar spectra with different frequencies in photothermal catalysis are urgently needed. Here, a hierarchical full-spectrum solar light utilization strategy is proposed. Based on this strategy, a Cu@hollow titanium silicalite-1 zeolite (TS-1) nanoreactor with spatially separated photo/thermal catalytic sites is designed to realize high-efficiency photothermal catalytic artificial photosynthesis. The space–time yield of alcohol products over the optimal catalyst reached 64.4 μmol g−1 h−1, with the selectivity of CH3CH2OH of 69.5%. This rationally designed hierarchical utilization strategy for solar light can be summarized as follows: (1) high-energy ultraviolet light is utilized to drive the initial and difficult CO2 activation step on the TS-1 shell; (2) visible light can induce the localized surface plasmon resonance effect on plasmonic Cu to generate hot electrons for H2O dissociation and subsequent reaction steps; and (3) low-energy near-infrared light is converted into heat by the simulated greenhouse effect by cavities to accelerate the carrier dynamics. This work provides some scientific and experimental bases for research on novel, highly efficient photothermal catalysts for artificial photosynthesis.
MXenes are a family of two-dimensional (2D) layered transition metal carbides/nitrides that show promising potential for energy storage applications due to their high-specific surface areas, excellent electron conductivity, good hydrophilicity, and tunable terminations. Among various types of MXenes, Ti3C2Tx is the most widely studied for use in capacitive energy storage applications, especially in supercapacitors (SCs). However, the stacking and oxidation of MXene sheets inevitably lead to a significant loss of electrochemically active sites. To overcome such challenges, carbon materials are frequently incorporated into MXenes to enhance their electrochemical properties. This review introduces the common strategies used for synthesizing Ti3C2Tx, followed by a comprehensive overview of recent developments in Ti3C2Tx/carbon composites as electrode materials for SCs. Ti3C2Tx/carbon composites are categorized based on the dimensions of carbons, including 0D carbon dots, 1D carbon nanotubes and fibers, 2D graphene, and 3D carbon materials (activated carbon, polymer-derived carbon, etc.). Finally, this review also provides a perspective on developing novel MXenes/carbon composites as electrodes for application in SCs.
Electrochemical C–C and C–N coupling reactions with the conversion of abundant and inexpensive small molecules, such as CO2 and nitrogen-containing species, are considered a promising route for increasing the value of CO2 reduction products. The development of high-performance catalysts is the key to the both electrocatalytic reactions. In this review, we present a systematic summary of the reaction systems for electrocatalytic CO2 reduction, along with the coupling mechanisms of C–C and C–N bonds over outstanding electrocatalytic materials recently developed. The key intermediate species and reaction pathways related to the coupling as well as the catalyst-structure relationship will be also discussed, aiming to provide insights and guidance for designing efficient CO2 reduction systems.
High-entropy materials (HEMs), which are newly manufactured compounds that contain five or more metal cations, can be a platform with desired properties, including improved electrocatalytic performance owing to the inherent complexity. Here, a strain engineering methodology is proposed to design transition-metal-based HEM by Li manipulation (LiTM) with tunable lattice strain, thus tailoring the electronic structure and boosting electrocatalytic performance. As confirmed by the experiments and calculation results, tensile strain in the LiTM after Li manipulation can optimize the d-band center and increase the electrical conductivity. Accordingly, the as-prepared LiTM-25 demonstrates optimized oxygen evolution reaction and hydrogen evolution reaction activity in alkaline saline water, requiring ultralow overpotentials of 265 and 42 mV at 10 mA cm−2, respectively. More strikingly, LiTM-25 retains 94.6% activity after 80 h of a durability test when assembled as an anion-exchange membrane water electrolyzer. Finally, in order to show the general efficacy of strain engineering, we incorporate Li into electrocatalysts with higher entropies as well.
Molybdenum disulfide (MoS2) has garnered significant attention in the field of catalysis due to the high density of active sites in its unique two-dimensional (2D) structure, which could be developed into numerous high-performance catalysts. The synthesis of ultra-small MoS2 particles (<10 nm) is highly desired in various experimental studies. The ultra-small structure could often lead to a distinct S–Mo coordination state and nonstoichiometric composition in MoSx, minimizing in-plane active sites of the 2D structure and making it probable to regulate the atomic and electronic structure of its intrinsic active sites on a large extent, especially in MoSx clusters. This article summarizes the recent progress of catalysis over ultra-small undoped MoS2 particles for renewable fuel production. Through a systematic review of their synthesis, structural, and spectral characteristics, as well as the relationship between their catalytic performance and inherent defects, we aim to provide insights into catalysis over this matrix that may potentially enable advancement in the development of high-performance MoS2-based catalysts for sustainable energy generation in the future.
The scarcity of wettability, insufficient active sites, and low surface area of graphite felt (GF) have long been suppressing the performance of vanadium redox flow batteries (VRFBs). Herein, an ultra-homogeneous multiple-dimensioned defect, including nano-scale etching and atomic-scale N, O co-doping, was used to modify GF by the molten salt system. NH4Cl and KClO3 were added simultaneously to the system to obtain porous N/O co-doped electrode (GF/ON), where KClO3 was used to ultra-homogeneously etch, and O-functionalize electrode, and NH4Cl was used as N dopant, respectively. GF/ON presents better electrochemical catalysis for VO2+/VO2+ and V3+/V2+ reactions than only O-functionalized electrodes (GF/O) and GF. The enhanced electrochemical properties are attributed to an increase in active sites, surface area, and wettability, as well as the synergistic effect of N and O, which is also supported by the density functional theory calculations. Further, the cell using GF/ON shows higher discharge capacity, energy efficiency, and stability for cycling performance than the pristine cell at 140 mA cm−2 for 200 cycles. Moreover, the energy efficiency of the modified cell is increased by 9.7% from 55.2% for the pristine cell at 260 mA cm−2. Such an ultra-homogeneous etching with N and O co-doping through “boiling” molten salt medium provides an effective and practical application potential way to prepare superior electrodes for VRFB.
