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The catalyst layers (CLs) electrode is the key component of the membrane electrode assembly (MEA) in proton exchange membrane fuel cells (PEMFCs). Conventional electrodes for PEMFCs are composed of carbon-supported, ionomer, and Pt nanoparticles, all immersed together and sprayed with a micron-level thickness of CLs. They have a performance trade-off where increasing the Pt loading leads to higher performance of abundant triple-phase boundary areas but increases the electrode cost. Major challenges must be overcome before realizing its wide commercialization. Literature research revealed that it is impossible to achieve performance and durability targets with only high-performance catalysts, so the controllable design of CLs architecture in MEAs for PEMFCs must now be the top priority to meet industry goals. From this perspective, a 3D ordered electrode circumvents this issue with a support-free architecture and ultrathin thickness while reducing noble metal Pt loadings. Herein, we discuss the motivation in-depth and summarize the necessary CLs structural features for designing ultralow Pt loading electrodes. Critical issues that remain in progress for 3D ordered CLs must be studied and characterized. Furthermore, approaches for 3D ordered CLs architecture electrode development, involving material design, structure optimization, preparation technology, and characterization techniques, are summarized and are expected to be next-generation CLs for PEMFCs. Finally, the review concludes with perspectives on possible research directions of CL architecture to address the significant challenges in the future.

While carbon dioxide (CO2) is a major greenhouse gas, it is also an important C1 resource. In the trend of energy conservation and emission reduction, electrocatalytic reduction has become a very promising strategy for CO2 utilization because it can convert CO2 directly to high-valued chemicals and fuels under mild conditions. In particular, the product CO and by-product H2 can be combined into syngas by an electrocatalytic CO2 reduction reaction (CO2RR) in an aqueous medium. Different molar ratios of CO and H2 may be used to produce essential bulk chemicals or liquid fuels such as methanol, alkanes, and olefins through thermochemical catalysis, Fischer–Tropsch synthesis, microbial fermentation, and other techniques. This work discusses the latest strategies in controlling the molar ratio of CO/H2 and improving the yield of CO2RR-to-syngas. The challenges of electrocatalytic syngas production are analyzed from an industrial application perspective, and the possible measures to overcome them are proposed in terms of new catalyst design, electrolyte innovation, flow reactor optimization, anodic reaction coupling, and operando technique application.

Urea is an essential fertilizer needed to meet the global demand for food. Currently, its production rate by reaction of carbon dioxide with ammonia is slow and the energy demand is high. Here we discuss strategies to overcome these challenges.

In the conversion process of syngas-to-C2 species, the OH species are inevitably produced accompanying the production of key intermediates CHx (x = 1–3), traditionally, the function of surface OH species is generally accepted as the hydrogenating reactive species. This work for the first time proposed and confirmed the assisted catalytic mechanism of surface OH species that performed as the promoter for syngas-to-C2 species on Cu-based catalysts. DFT and microkinetic modeling results reveal that the produced OH species accompanying the intermediates CHx production on the MCu (M = Co, Fe, Rh) catalysts can stably exist to form OH/MCu catalysts, on which the presence of surface OH species as the promoter not only presented better activity and selectivity toward CHx (x = 1–3) compared to MCu catalysts, but also significantly suppressed CH3OH production, providing enough CHx sources to favor the production of C2 hydrocarbons and oxygenates. Correspondingly, the electronic properties analysis revealed the essential relationship between the electronic feature of OH/MCu catalysts and catalytic performance, attributing to the unique electronic micro−environment of the catalysts under the interaction of surface OH species. This new mechanism is called as OH-assisted catalytic mechanism, which may be applied in the reaction systems related to the generation of OH species.

A convenient method for methane (CH4) direct conversion to methanol (CH3OH) is of great significance to use methane-rich resources, especially clathrates and stranded shale gas resources located in remote regions. Theoretically, the activation of CH4 and the selectivity to the CH3OH product are challenging due to the extreme stability of CH4 and relatively high reactivity of CH3OH. The state-of-the-art ‘methane reforming - methanol synthesis’ process adopts a two-step strategy to avoid the further reaction of CH3OH under the harsh conditions required for CH4 activation. In the electrochemical field, researchers are trying to develop conversion pathways under mild conditions. They have found suitable catalysts to activate the C–H bonds in methane with the help of external charge and have designed the electrode reactions to continuously generate certain active oxygen species. These active oxygen species attack the activated methane and convert it to CH3OH, with the benefit of avoiding over-oxidation of CH3OH, and thus obtain a high conversion efficiency of CH4 to CH3OH. This mini-review focuses on the advantages and challenges of electrochemical conversion of CH4 to CH3OH, especially the strategies for supplying electro-generated active oxygen species in-situ to react with the activated methane.

C2H2 semi-hydrogenation has been widely applied in industry to eliminate trace C2H2 from C2H4 feed. C2H2 semi-hydrogenation to C2H4 on a series of the newly designed catalysts, graphdiyne (GDY) as a new carbon allotrope supported different sizes of PdxMy clusters (PdxMy/GDY, M = Cu, Ag, Au, Ni; x+y = 1–3), were studied using DFT calculations. The results found that C2H2 semi-hydrogenation to C2H4 on PdxMy/GDY catalysts exhibits that both the activity and selectivity greatly depend on the composition and size of PdxMy/GDY catalysts. Surprisingly, our results for the first time discovered the Pd1/GDY catalyst with GDY supported the single atom Pd that presents the best selectivity and activity toward C2H4 formation compared to the previously reported catalysts so far in C2H2 semi-hydrogenation. This study would provide a theoretical clue for designing and screening out the potential catalysts with GDY supported small sizes of PdxMy and other metal clusters in C2H2 hydrogenation.

Abstract Ionic liquids (ILs) have been used for carbon dioxide (CO2) capture, however, which have never been used as catalysts to accelerate CO2 capture. The record is broken by a uniquely designed IL, [EMmim][NTf2]. The IL can universally catalyze both CO2 sorption and desorption of all the chemisorption‐based technologies. As demonstrated in monoethanolamine (MEA) based CO2 capture, even with the addition of only 2000 ppm IL catalyst, the rate of CO2 desorption—the key to reducing the overall CO2 capture energy consumption or breaking the bottleneck of the state‐of‐the‐art technologies and Paris Agreement implementation—can be increased by 791% at 85 °C, which makes use of low‐temperature waste heat and avoids secondary pollution during CO2 capture feasible. Furthermore, the catalytic CO2 capture mechanism is experimentally and theoretically revealed.

Abstract In addition to being used as an energy source, coal also has significant potential for other, more sustainable uses including water treatment. In this study, we present a simple approach to treat water that was produced during oil production and contained a total dissolved solids (TDS) content of over 150 g/L using Powder River Basin (PRB) coal. PRB coal used as packing material in a flow-through column effectively removed 60%–80% of the cations and anions simultaneously. Additionally, 71%–92% of the total organic carbon in the produced water was removed as was all of the total suspended solids. The removal mechanisms of both cations and anions were investigated. Cations were removed by ion exchange with protons from oxygen-containing functional groups such as carboxylic and phenolic hydroxyl groups. Anions, mainly Cl−1, appeared to be removed through either the formation of resonance structures as a result of delocalization of electrons within coal molecules or through ion–π interactions. We propose that coal is a “pseudo-amphoteric” exchange material that can remove cations and anions simultaneously by exchanging ions with both ionized and non-ionized acids that are ubiquitous in coal structure or resonance effect. Graphical abstract

Abstract Methane (CH4) is inexpensive, high in heating value, relatively low in carbon footprint compared to coal, and thus a promising energy resource. However, the locations of natural gas production sites are typically far from industrial areas. Therefore, transportation is needed, which could considerably increase the sale price of natural gas. Thus, the development of distributed, clean, affordable processes for the efficient conversion of CH4 has increasingly attracted people's attention. Among them are plasma technology with the advantages of mild operating conditions, low space need, and quick generation of energetic and chemically active species, which allows the reaction to occur far from the thermodynamic equilibrium and at a reasonable cost. Significant progress in plasma‐assisted reforming of methane (PARM) is achieved and reviewed in this paper from the perspectives of reactor development, thermal and nonthermal PARM routes, and catalysis. The factors affecting the conversion of reactants and the selectivity of products are studied. The findings from the past works and the insight into the existing challenges in this work should benefit the further development of reactors, high‐performance catalysts, and PARM routes.

Coagulation is the most widely used method in the treatment of printing and dying wastewater. To better understand the relationship between the coagulation effect and dye molecular structures, quantitative structure activity relationship (QSAR) analyses were performed to elucidate the factors affecting the coagulation in ferric chloride (FeCl3) coagulation process. First, the coagulation experiments on 38 dye molecules were conducted to determine their color removal rates (Rexp) by FeCl3 under different pH conditions (i.e., pH = 4 and 10). The results showed that the average Rexp of dyes were 41.36% ± 2.40% at pH value of 4 and 55.70% ± 2.83% at pH value of 10. Subsequently, a multiple linear regression (MLR) method was used to construct QSAR models based on Rexp and 42 molecular parameters calculated by Gaussian 09, Materials Studio 7.0 and Multiwfn. The developed QSAR models exhibited excellent stability, reliability, and robustness with values of R2 = 0.7950, 0.8170, Q2INT = 0.6401, 0.7382, Q2EXT = 0.5168, 0.5441, at pH values of 4 and 10, respectively. Through analysis of quantum parameter values, electrostatic adsorption and hydrogen bonding adsorption were primarily responsible for the coagulation process. Therefore, this study could be useful in providing critical information for evaluating the removal efficiency and a feasible way to predict the removal rate of dyes by FeCl3 when no coagulation experiments were conducted.

The purpose of this study was to prepare a proof-of-concept CO2 adsorbing material based on a new amine grafted silica aerogel microsphere (AGSAM) that could be used on both fixed and fluidized beds. A low-cost water glass and environment-friendly water were used as precursor and solvent of the silica aerogel, respectively. The silica aerogel microsphere (SAM) was prepared by dropping the siliceous solution into hot oil bath. The effect of the pH value of the siliceous solution, stirring speed and stirring paddle position on the sphericity and size of the SAM was investigated. The SAM with good sphericity was obtained when the pH value was 5.69–5.79. The mean diameter of the SAM decreased from 5 to 1 mm when the stirring speed increased from 1000 to 2000 rpm. The SAM with excellent sphericity was prepared when the paddle was placed on the top of the oil bath. When the paddle was placed at the middle and bottom of the oil bath, some liquid drops aggregated together and formed large aggregations. AGSAM was obtained by grafting the amine groups onto the framework of the silica gel microsphere. The CO2 adsorption capacity of the AGSAM was 1.04 mmol g-1 with 1% CO2 at 300 mL min-1. The AGSAM with 4, 3.2, 2 and 1 mm in diameters had the fluidizing velocities of 0.531, 0.425, 0.265 and 0.159 m s-1, respectively. The AGSAM with different sizes met different fluidizing conditions.

With the shape selective zeolite catalyst, toluene alkylation with methanol to para-xylene (MTPX) technology could produce highly pure para-xylene (PX) in one step. The lower feedstock cost and less energy consumption in products separation make it more competitive compared to the current toluene disproportionation route. Thus, MTPX is regarded as the most reasonable production route for PX production. This article reviews the strategies that applied to the preparation of high-performance catalysts for MTPX, with special focus on the precise control of pore dimension and acid sites distribution in zeolite to achieve the highest selectivity to PX. The outlook of the MTPX catalyst is also proposed to guide the catalyst development in the field.

Abstract In this study, the Powder River Basin (PRB) coal fast pyrolysis was conducted at 700 °C in the atmosphere of syngas produced by CH4–CO2 reforming in two different patterns, including the double reactors pattern (the first reactor is for syngas production and the second is for coal pyrolysis) and double layers pattern (catalyst was at upper layer and coal was at lower layer). Besides, pure gases atmosphere including N2, H2, CO, H2–CO were also tested to investigate the mechanism of the coal pyrolysis under different atmospheres. The pyrolysis products including gas, liquid and char were characterized, the result showed that, compared with the inert atmosphere, the tar yield is improved with the reducing atmospheres, as well as the tar quality. The hydrogen partial pressure is the key point for that improvement. In the atmosphere of H2, the tar yield was increased by 31.3% and the contained BTX (benzene, toluene and xylene) and naphthalene were increased by 27.1% and 133.4%. The double reactors pattern also performed outstandingly, with 25.4% increment of tar yield and 25.0% and 79.4% for the BTX and naphthalene. The double layers pattern is not effective enough due to the low temperature (700 °C) in which the Ni-based catalyst was not fully activated.

Carbon dioxide (CO2) capture and conversion provide an alternative approach to synthesis of useful fuels and chemicals. Here, Ye et al. give a comprehensive perspective on the current state of the art and outlook of CO2 catalytic hydrogenation to the synthesis of light olefins, dimethyl ether, liquid fuels, and alcohols.

This work developed a cost-effective and environmentally benign method for preparing high electrical conductivity carbon nanofibers (CNFs) from coal extraction residuals. The electrical conductivity of the CNFs prepared with PAN and 10.00 wt%, 30.00 wt%, and 50.00 wt% residual extracted tar (RET) increases by 70.89%, 164.31%, and 193.22% in comparison with conventional pure PAN-based CNF at the carbonization temperature of 1000 °C. The results of electrochemical impedance spectroscopy have shown that the total resistance for 50.00 wt% and 30.00 wt% RET-based CNFs prepared at the reaction temperature of 1000 °C was 0.61 Ω and 0.73 Ω, respectively, which is lower than that of coal extracted tar (CET)-based CNF and PAN-based CNFs. Raman analysis indicates that the 50.00 wt% RET-based CNF shows the lowest relative intensity of −0.953 and the highest degree of the ordered carbon structure. According to SEM results, fewer defects were observed in the carbon structure of RET-based CNFs. The cross-linking structure in 50.00 wt% RET can contribute to the improvement of the electrical conductivity of CNFs, which is consistent with the observation of Raman results. The GC-MS analysis results reveal that the aromatic and phenolic concentration in RET is 37.91% and 176.69% higher compared with those in CET. Both aromatic and phenolic concentrations in CNF precursor favor the formation of CNFs with fewer defects and thus lead to a higher electrical conductivity in CNF. The GC-MS results present consistency with those of Raman, SEM, and electrochemical performance measurements.

Biomass furfural-like compounds are chemicals that cannot be extracted from fossil materials, through which a large number of fine chemicals and fuel additives can be opened up, but one big efficiency problem during the transformation is the accumulation of oligomers. Here, we propose a novel and efficient Ru-Mo bimetallic catalyst for selective hydrogenation-rearrangement of furfural-like compounds. The result showed that an unprecedented rearrangement product selectivity of 89.1% to cyclopentanol was achieved under an optimized reaction condition over a 1%Ru−2.5%Mo/CNT catalyst reduced at 600°C. Subsequent characterization suggested that the catalyst presented with weak acidity and strong hydrogenation activity for the reaction, which not only ensures the smooth hydrogenation-rearrangement reaction but also inhibits the accumulation of furan polymers. These findings provide a convenient strategy to tune the catalytic performance of Mo-based catalysts by controlling the reduction and carburization conditions, which appear to be versatile for the rearrangement of furans and similar compounds.

Summary: Solar pyrolysis of renewable biomass has huge potential for sustainable production of fuel or chemical feedstock for the activated carbon materials. Here, we report a method for producing high-quality carbon nanofiber (CNF) precursor and subsequently CNFs as a low-cost and eco-friendly energy storage material. Specifically, pinewood is pyrolyzed with solar energy to generate a phenol-rich bioliquid precursor that is found to be a strong candidate for synthesizing binder-free flexible electrode materials via electrospinning. The CNFs prepared with 30% solar-driven bioliquids and 70% polyacrylonitrile have a high specific surface area and rich microstructure, which are the key to its electrochemical performance in terms of specific capacitance (349 F g−1 at the current density of 0.5 A g−1) with notable rate performance, reversibility, and cycling stability in 6 M KOH aqueous electrolyte. Thus, solar bioliquids are feasible CNF precursors, and such derived CNFs have potential to be applied in energy storage devices.

The notoriously slow kinetics in CO2 desorption hinders the development of efficient CO2 capture technologies. Here, the authors discover that nanostructured TiO(OH)2 as a catalyst is capable of dramatically increasing the rates of CO2 desorption from spent monoethanolamine.

Abstract The objective is to find a new pathway for significant reduction in CO2 capture energy consumption. Specifically, nanoporous TiO(OH)2 was used to realize the objective, which was desired as a catalyst to significantly accelerate the decomposition of aqueous NaHCO3, essentially CO2 desorption – the key step of Na2CO3/NaHCO3 based CO2 capture technologies from overall CO2 energy consumption perspective. Effects of several important factors on TiO(OH)2-catalyzed NaHCO3 decomposition were investigated. The quantity of CO2 generated from 0.238 mol/L NaHCO3 at 65 °C with catalyst is ~800% of that generated without the presence of catalyst. When a 12 W vacuum pump was used for carrying the generated CO2 out of reactor, the total amount of CO2 released was improved by ~2,500% under the given experimental conditions. No significant decrease in the catalytic effect of TiO(OH)2 was observed after five cyclic CO2 activated tests. In addition, characterizations with in-situ Fourier transform infrared spectroscopy, thermal gravity analysis and Brunauer-Emmett-Teller of TiO(OH)2 indicate that TiO(OH)2 is quite stable. The discovery in this research could inspire scientists’ interests in starting to focus on a new pathway instead of making huge effort or investment in designing high-capacity but expensive CO2 sorbent for developing practical or cost-effective CO2 technologies.

Lithium (Li) is an important strategic resource, and with the increasing demand for Li, there are some limitations in the exploitation and utilization of conventional deposits such as the pegmatite-type and brine-type Li deposits. Therefore, it has become imperative to search for Li from other sources. Li in coal is thought to be one of the candidates. In this study, the petrology, mineralogy, and geochemistry of No. 21 coal from the Hebi No. 6 mine, Anhe Coalfield, China, was reported, with an emphasis on the distribution, modes of occurrence, and origin of Li. The results show that Li is enriched in the No. 21 coal, and its concentration coefficient (CC) value is 6.6 on average in comparison with common world coals. Lithium in the studied coal is mainly present in aluminosilicates, mainly clay minerals, some of which contain a significant amount of Ti. The Li enrichment in the No. 21 coal is mainly controlled by the terrigenous materials and sourced from the moyite of the Yinshan Upland. Furthermore, Li in the No. 21 coal is more enriched in coals formed in acidic and humid conditions and coals influenced by fresh water during peat accumulation.

Theoretical investigation of the static and kinetic behaviors of H and H2 on metal surface plays a key role in the development of hydrogenation catalysts and new materials with high H2 storage capacity. Based on the density functional theory (DFT) calculation of H and H2 adsorption on Pt(111), H(a) adatom strongly interacts with surface Pt; while H2 weakly adsorbs on Pt(111). H(a) adatoms stably occupy the face-centered cubic sites on Pt(111) which agrees with the experimental LERS observations. By using kinetic Monte Carlo (kMC) simulation, the qualitative effects of the kinetic parameters on the H2 TDS spectra indicate that the H2 desorption peaks shift to the low temperature with increasing pre-exponential factor and decreasing desorption barrier. Simultaneously, the desorption peaks shift downwards and broaden to two peaks with the increase of the lateral interaction energy among H(a) adatoms. Using the kMC simulation based on DFT calculation, the predicted H2 TDS spectra are well consistent with the experimental ones. It unanimously proves that the two peaks of TDS spectra are derived from the lateral interactions among H(a). This work provides the intrinsic kinetics of H(a) and H2 on Pt(111) at an atomic level, and gives insight into the development of hydrogenation catalysts.

Emerging contaminants (ECs) have drawn attention to many countries due to their persistent input and potential threat to human health and the environment. This article reviews the current contamination sources and their status for surface waters in China. The contamination levels of ECs in surface waters are in the range ng L ^−1 to μ g L ^−1 in China, apparently about the same as the situation in other countries. ECs enter surface water via runoff, drainage, rainfall, and wastewater treatment effluent. The frequency of occurrence of ECs increased rapidly from 2006 to 2011; a significant reason is the production and consumption of pharmaceuticals and personal care products. As for the distribution of EC pollution in China, the frequency of occurrence of ECs in eastern regions is higher than in western regions. A majority of EC studies have focused on surface waters of the Haihe River and Pearl River watersheds due to their highly developed industries and intense human activity. Legislative and administrative regulation of ECs is lacking in China. To remove ECs, a number of technologies, such as absorption by activated carbon, membrane filtration technology, and advanced oxidation processes, have been researched.

While carbon dioxide (CO2) is a major greenhouse gas, it is also an important C1 resource. In the trend of energy conservation and emission reduction, electrocatalytic reduction has become a very promising strategy for CO2 utilization because it can convert CO2 directly to high-valued chemicals and fuels under mild conditions. In particular, the product CO and by-product H2 can be combined into syngas by an electrocatalytic CO2 reduction reaction (CO2RR) in an aqueous medium. Different molar ratios of CO and H2 may be used to produce essential bulk chemicals or liquid fuels such as methanol, alkanes, and olefins through thermochemical catalysis, Fischer-Tropsch synthesis, microbial fermentation, and other techniques. This work discusses the latest strategies in controlling the molar ratio of CO/H2 and improving the yield of CO2RR-to-syngas. The challenges of electrocatalytic syngas production are analyzed from an industrial application perspective, and the possible measures to overcome them are proposed in terms of new catalyst design, electrolyte innovation, flow reactor optimization, anodic reaction coupling, and operando technique application. [ABSTRACT FROM AUTHOR]