Three large π-conjugated and imine-based COFs,named TFP-TAB,TFP-TTA,and TTA-TTB,were synthesized via the ordered incorpo-ration of benzene and triazine rings in the same host framework to study how the structural units affect the efficiency of CO2 photoreduction.Results from both experiments and density-functional theory(DFT)calculations indicate the separation and transfer of the photoinduced charges is highly related to the triazine-N content and the conjugation degree in the skeletons of COFs.High-efficiency CO2 photoreduction can be achieved by rationally adjusting the number and position of both benzene and triazine rings in the COFs.Specifically,TTA-TTB,with orderly interlaced triazine-benzene heterojunctions,can suppress the recombination probability of electrons and holes,which effectively immobilizes the key species(COOH)and lowers the free energy change of the potential-determining step,and thus exhibits a superior visible-light-induced photocatalytic activity that yields 121.7 μmol HCOOH g-1 h-1.This research,therefore,helps to elucidate the effects of the different structural blocks in COFs on inherent heterogeneous photocatalysis for CO2 reduction at a molecular level.

Understanding processing-structure-property (PSP) linkages of solid-phase microextraction (SPME) coating materials is crucial for the rational design and advancement of these new materials. As SPME is a diffusion-based extraction technique, analyzing the morphology of its coating materials is important for optimizing its performance. In this study, we assess the morphological evolution of micro/mesoporous amorphous silicon (a-Si) thin films sputtered at an oblique angle onto silicon, which serve as models for support materials in SPME devices. The contrast of scanning transmission electron microscopy (STEM) images is enhanced via ZnO infiltration by atomic layer deposition (ALD). Various metrics, including physical descriptors and two-point statistics methods, are employed to follow the films' evolution. Analysis of the two-point correlation function reveals a simple ellipse/spherical local pore geometry in contrast to the long-range irregular arrangement of pores identified by a range of traditional and novel metrics. Additionally, analyzing the internal structure of the pores through homology metrics aligns well with the theoretical understanding of morphological evolution in oblique sputtered films. These analyses show that the "average ratio of principal moment of inertia", "Betti numbers", and "two-point statistics" based metrics can capture valuable information during film growth. The morphological analysis approach proposed in this study can be applied to analyze any nanoporous medium as a first step towards developing structure-property relationships that tie back to a given preparation method. Ultimately, a more extensive experimental and/or simulation-based study should confirm the correlations between these metrics and actual diffusion properties as the basis for process-structure-properties relations for improved design and optimization of this film.

Surface silanols (Si-OH) play a vital role on fused silica surfaces in chromatography. Here, we used an atmospheric-pressure, gas-phase reactor to modify the inner surface of a gas chromatography, fused silica capillary column (0.53 mm ID) with a small, reactive silane (tris(dimethylamino)methylsilane, TDMAMS). The deposition of TDMAMS on planar witness samples around the capillary was confirmed with X-ray photoelectron spectroscopy (XPS), ex situ spectroscopic ellipsometry (SE), and wetting. The number of surface silanols on unmodified and TDMAMS-modified native oxide-terminated silicon were quantified by tagging with dimethylzinc (DMZ) via atomic layer deposition (ALD) and counting the resulting zinc atoms with high sensitivity-low energy ion scattering (HS-LEIS). A bare, clean native oxide – terminated silicon wafer has 3.66 OH/nm2, which agrees with density functional theory (DFT) calculations from the literature. After TDMAMS modification of native oxide-terminated silicon, the number of surface silanols decreases by a factor of ca. 10 (to 0.31 OH/nm2). Intermediate surface testing (IST) was used to characterize the surface activities of functionalized capillaries. It suggested a significant deactivation/passivation of the capillary with some surface silanols remaining; the modified capillary shows significant deactivation compared to the native/unmodified fused silica tubing. We believe that this methodology for determining the number of residual silanols on silanized fused silica will be enabling for chromatography.

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.

Ammonia, primarily made with Haber-Bosch process developed in 1909 and winning two Nobel prizes, is a promising noncarbon fuel for preventing global warming of 1.5 °C above pre-industrial levels. However, the undesired characteristics of the process, including high carbon footprint, necessitate alternative ammonia synthesis methods, and among them is chemical looping ammonia production (CLAP) that uses nitrogen carrier materials and operates at atmospheric pressure with high product selectivity and energy efficiency. To date, neither a systematic review nor a perspective in nitrogen carriers and CLAP has been reported in the critical area. Thus, this work not only assesses the previous results of CLAP but also provides perspectives towards the future of CLAP. It classifies, characterizes, and holistically analyzes the fundamentally different CLAP pathways and discusses the ways of further improving the CLAP performance with the assistance of plasma technology and artificial intelligence (AI).

We demonstrate the development of a new atmospheric pressure-atomic layer deposition(AP-ALD) system to coat the inner walls of capillary columns for gas chromatography (GC). Unlike traditional ALD, this reactor operates at near-atmospheric pressure and addresses the challenges of depositing thin films inside capillaries, which include long pump down times, deposition in high-aspect-ratio materials, and temperature control. We show ALD of alumina in 5 and 12 m capillaries (0.53 mm ID) via sequential half reactions of trimethylaluminum and water. Our system yields pinhole-free, uniform thin films. It includes small witness chambers for witness silicon shards before and after the capillary. An engineering flow/transport analysis of the device is provided. Our ALD alumina thin films are characterized by spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy. Alumina film growth achieved is 1.4-1.5 Å/cycle, which is consistent with previously reported results. Film thickness measurements by SE on witness shards of silicon and by TEM at both ends of the capillary are in good agreement. A capillary column coated with alumina is used to separate different gases by GC, although the retention times of gases are essentially the same as with an untreated fused silica capillary. This successful deposition of ALD alumina in long capillaries opens the door for other possible ALD coatings, including hybrid organic-inorganic coatings, using the 450+ ALD precursors available today.

Chemical looping ammonia generation (CLAG) is a promising NH3 production technology due to its potential for high yield of NH3 and low CO2 emission footprint. However, the stabilities of the existing N-carriers are problematic during the cyclic N-sorption/desorption. This research was designed to overcome that challenge through use of elemental doping and depositing the N-carrier on a support. The experimental results show that the N-sorption/desorption performance of gamma-Al2O3 N-carriers decreased with cycling due to the deterioration of the pore structure and phase transformation. A Si-modified alumina-based N-carrier, with a Si: Al molar ratio of 1:20 prepared by co-precipitation, was much more resistant to high-temperature phase transition and collapse of pore structure, resulting in highly stable cyclic N-sorption/desorption performance. Use of ZrO2 as a support for the Si-modified Al-based N-carrier further reduced NH3 decomposition and thus increased the NH3 yield and selectivity by 85.6% and 53.6% compared to that obtained with the pure gamma-Al2O3 N-carrier.

Atomic layer deposition (ALD) is widely used in the semiconductor and materials industries for depositing thin films. Here, we describe a holder/container for performing ALD on particles that does not require agitation. This device contains a broad, shallow, circular recess that holds the particles. Two different frits and combinations of stacked meshes were explored as a cover to this holder to restrict the movement of the particles while still allowing good conductance of the ALD reagent gases. A mathematical discussion of the diffusion through the frits and stacked meshes is presented. As confirmed by spectroscopic ellipsometry (SE) on planar witness silicon shards, consistent, high‐quality film growth took place inside and outside the holder. The performance of the holder was demonstrated with ~5‐μm zirconia particles that were coated with alumina from trimethylaluminum (TMA) and water, and with zinc oxide from diethylzinc (DEZ) and water. Deposition on different amounts of particles was investigated (50, 100, 200, and 500 mg). Parasitic chemical vapor deposition (CVD) appeared to be present when a greater number of particles or meshes were used. ALD coating on particles was also confirmed by X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and energy‐dispersive X‐ray spectroscopy (EDS).

Plasma technology is an eco-friendly way to modify or fabricate carbon-based materials (CBMs) due to plasmas' distinctive abilities in tuning the surface physicochemical properties by implanting functional groups or incorporating heteroatoms into the surface without changing the bulk structure. However, the mechanisms of functional groups formation on the carbon surface are still not clearly explained because of the variety of different discharge conditions and the complexity of plasma chemistry. Consequently, this paper contains a comprehensive review of plasma-treated carbon-based materials and their applications in environmental, materials, and energy fields. Plasma-treated CBMs used in these fields have been significantly enhanced in recent years because these related materials possess unique features after plasma treatment, such as higher adsorption capacity, enhanced wettability, improved electrocatalytic activity, etc. Meanwhile, this paper also summarizes possible reaction routes for the generation of functional groups on CBMs. The outlook for future research is summarized, with suggestions that plasma technology research and development shall attempt to achieve precise control of plasmas to synthesize or to modify CBMs at the atomic level.

CO 2 reduction under simulated sunlight over photocatalysts has become an attractive researcher area recently.In this work,carbon nitride compounds modified by TiO 2 nanoparticles（TNPs） have been used for the photoreduction of CO 2 in the presence of CH 4 at room temperature.Briefly,a series of noble-metal-free TNP-graphitic-carbon nitride（g-C 3 N 4 ,also abbreviated CN） photocatalysts with different TNPs loadings and calcination temperatures have been synthesized by a wet-chemical method.The characterization results of XRD,FTIR,SEM,TEM,BET,XPS,CO 2 Adsorption,UV-vis,and PL demonstrate that the BET surface area and CO 2 adsorption capacity have been improved after the calcination.Besides,the g-C 3 N 4 has been successfully coupled with the TNPs and a heterojunction has formed at their interface.These characters contribute to increase the photocatalytic activity of TNPs-CN toward reducing CO 2 in the presence of CH 4 ,and its’ performance is better than bare g-C 3 N 4 ,Titania(P 25 )-CN,MgO-CN,or Cu 2 O-CN.Orthogonal experiments are then carried out to investigate the sensitivity factors and optimum conditions.The sensitivity results show that the reaction pressure makes little difference on the photocatalysis results,which verifies the photoinduced CO 2 -CH 4 reaction has a tiny change in gas volume.In addition,under the optimum conditions,the turnover frequency（TOF） of CO after 4 h reaction can reach 9.98 μmol g-cat. -1 h -1 ,and traces of ethane and ethylene have been detected during the reactions.In addition,surface acetate and carbonaceous deposit are found on the（20）TNPs-CN/450 surface after continuous 24 h irradiation under the optimum conditions,which resulting in the inactivation of the catalyst.Finally,possible reaction mechanisms have been proposed based on the results.

Strong interactions between Fe–Cu–K and SAPO-34 in admixed catalysts composed of Fe–Cu–K and SAPO-34 result in the changes of structures, reducible properties and mass transfer between Fe-Cu-K and SAPO-34, which contribute to good activities.

In order to decrease the electricity consumption of hydrogen generation, hydrazine-assisted water electrolysis is intensively investigated recently. Herein, hierarchical nanostructure of ultrathin NiCo(OH)(x)nanosheets (NSs) that in-situ grown on the NiCoP nanowires (NWs) was deposited on nickel foam (NF) to construct NiCo(OH)(x)@NiCoP/NF electrode. NiCoP NWs extend the surface area, spatial utilization of NF and enhance the electron conduction to the outmost NiCo(OH)(x)NSs. NiCo(OH)(x)NSs interlace to form regular mesoporous channels, which improve the structural stability and mass transfer rate. Moreover, NiCoP NWs enhance the adsorption of protons and the transfer of electrons, while NiCo(OH)(x)NSs facilitate the adsorption of OH(ad)during reaction. As a result, NiCo(OH)(x)@NiCoP/NF exhibits excellent activity for both hydrazine oxidation reaction (HzOR) and hydrogen evolution reaction (HER). Based on the NiCo(OH)(x)@NiCoP/NF||NiCo(OH)(x)@NiCoP/NF couples, electrolysis of hydrazine for hydrogen generation only requires an extremely low cell voltage of 0.03 V.

Direct synthesis of dimethyl ether (DME) by CO2 hydrogenation has been investigated over three hybrid catalysts prepared by different methods: co-precipitation, sol-gel, and solid grinding to produce mixed Cu, ZnO, ZrO2 catalysts that were physically mixed with a commercial ferrierite (FER) zeolite. The catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption of CO2 (CO2-TPD), temperature programmed desorption of NH3 (NH3-TPD), and temperature programmed H2 reduction (H2-TPR). The results demonstrate that smaller CuO and Cu crystallite sizes resulting in better dispersion of the active phases, higher surface area, and lower reduction temperature are all favorable for catalytic activity. The reaction mechanism has been studied using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Methanol appears to be formed via the bidentate-formate (b-HCOO) species undergoing stepwise hydrogenation, while DME formation occurs from methanol dehydration and reaction of two surface methoxy groups.

This research is designed to make progress in overcoming the challenges through the development of a two-stage coal processing. Specifically, a two-stage process was used to maximize the use of the carbon in coal or increase the carbon monoxide yield or lower carbon dioxide and methane yields. Carbon dioxide-char gasification in the absence of water can generate carbon monoxide with near-zero methane, which is desired to produce high-carbon and low-hydrogen chemicals such as oxalic acid through catalytic carbon monoxide coupling and hydrolysis. The technology is applicable to any coal, although Power River Basin (PRB) coal is used as an example feedstock in this research Also, the sodium-iron catalyst can accelerate not only the reaction kinetics in both stages but also increase the hydrogen/carbon monoxide ratio in the syngas produced in the second stage. In other words, the catalyst is a multifunctional agent, which can not only intensify the overall coal process efficiency but also improve the qualities of the desired syngas products and reduce carbon dioxide emission. Thus, In the 1st stage, the catalysts can significantly reduce the CO2-char gasification by as high as 75.00%. In the 2nd stage, the H2/CO ratio of ideal syngas is ∼2:1 with near-0 CH4 generation and the CH4 production can be reduced as high as 61.29% for the CO2–H2O-Char coal gasification. The activation energy for the 2nd stage is reduced by as high as 35.43% than that of raw coal without use Na–Fe catalyst. The overall carbon footprint reduction for the study is reduced by 87.33% in the 1st stage and 96.77% compared to the direct coal combustion.

The production of ethylene via the oxidative dehydrogenation of ethane is well-documented as an energy efficient process. Alumina-supported NiO catalysts make the oxidative dehydrogenation of ethane more selective to ethylene and operate at low reaction temperatures (<500 degrees C). The addition of silica to the alumina supports of these NiO catalysts formed higher amounts of the NiAl2O4 spinel phase and had adjustable acidities and surface areas with calcination temperature, leading to increases in ethylene productivity. A 5 wt% silica-doped alumina support calcined at 1100 degrees C with 16 wt% NiO exhibited low acidity and a stable, low surface area, resulting in an ethylene productivity of 13.6 mu mol(ethylene)/s.g(nickel) or 1.32 x 10(-2) mu mol(ethylene)/s.m(2) at 500 degrees C.

This comprehensive critical review combines, for the first time, recent advances in nanoscale surface chemistry, surface science, DFT, adsorption calorimetry, and in situ XRD and TEM to provide new insights into catalyst sintering. This work provides qualitative and quantitative estimates of the extent and rate of sintering as functions of nanocrystal (NC) size, temperature, and atmosphere. This review is unique in that besides summarizing important, useful data from previous studies, it also advances the field through addition of (i) improved or new models, (ii) new data summarized in original tables and figures, and (iii) new fundamental perspectives into sintering of supported metals and particularly of chemical sintering of supported Co during Fischer-Tropsch synthesis. We demonstrate how the two widely accepted sintering mechanisms are largely sequential with some overlap and highly NC-size dependent, i.e., generally, small NCs sinter rapidly by Ostwald ripening, while larger NCs sinter slowly by crystallite migration and coalescence. In addition, we demonstrate how accumulated knowledge, principles, and recent advances, discussed in this review, can be utilized in the design of supported metal NCs highly resistant to sintering. Recommendations for improving the design of sintering experiments and for new research are addressed.

This comprehensive critical review combines, for the first time, recent advances in nanoscale surface chemistry, surface science, DFT, adsorption calorimetry, and in situ XRD and TEM to provide new insights into catalyst sintering. This work provides qualitative and quantitative estimates of the extent and rate of sintering as functions of nanocrystal (NC) size, temperature, and atmosphere. This review is unique in that besides summarizing important, useful data from previous studies, it also advances the field through addition of (i) improved or new models, (ii) new data summarized in original tables and figures, and (iii) new fundamental perspectives into sintering of supported metals and particularly of chemical sintering of supported Co during Fischer-Tropsch synthesis. We demonstrate how the two widely accepted sintering mechanisms are largely sequential with some overlap and highly NC-size dependent, i.e., generally, small NCs sinter rapidly by Ostwald ripening, while larger NCs sinter slowly by crystallite migration and coalescence. In addition, we demonstrate how accumulated knowledge, principles, and recent advances, discussed in this review, can be utilized in the design of supported metal NCs highly resistant to sintering. Recommendations for improving the design of sintering experiments and for new research are addressed.

The aim of the present work is to provide a preliminary support and research foundation for developing integrated technology of methane dry reforming and pine wood pyrolysis to produce high value chemicals and fuels. The chemical properties of bio-oil produced by pine wood pyrolysis under tradi-tional N-2, H-2, CO2, CH4 atmospheres and mixtures of CH4 and CO2 were investigated. Experimental studies were conducted in a fixed bed reactor at a temperature of 500 degrees C. The results show that pine wood pyrolysis under mixtures of methane and CO2 can promote bio-oil production (0.98% increase) compared with traditional pyrolysis (under N-2). GC-MS results show that the contents of phenols and sugars in bio-oil decreased, while the amount of alcohols, aldehydes, ketones, and furans increased. NMR spectroscopy provides additional support of the results. Results indicate that bio-oil can be used as a source of value-added chemicals. High proportions of CO were obtained in the gas products from pine wood pyrolysis under CH4 and mixtures of CH4 and CO2. Finally, a possible reaction pathway of pine wood pyrolysis under mixtures of methane and CO2 is proposed. Methane bi-reforming with CO2 and steam from pine wood pyrolysis could promote the production of high value oxygen-containing chemicals during pine wood pyrolysis under mixtures of CH4 and CO2. (C) 2020 Elsevier Ltd. All rights reserved.

Recently, carbon dioxide capture and conversion, along with hydrogen from renewable resources, provide an alternative approach to synthesis of useful fuels and chemicals. People are increasingly interested in developing innovative carbon dioxide hydrogenation catalysts, and the pace of progress in this area is accelerating. Accordingly, this perspective presents current state of the art and outlook in synthesis of light olefins, dimethyl ether, liquid fuels, and alcohols through two leading hydrogenation mechanisms: methanol reaction and Fischer-Tropsch based carbon dioxide hydrogenation. The future research directions for developing new heterogeneous catalysts with transformational technologies, including 3D printing and artificial intelligence, are provided.

Coal is a rich-in-C and poor-in-H material. How should we maximize uses of C and H in coal for producing desired gases eventually converted to liquid chemicals with minimal CO2 emission? This research is designed to make progress in overcoming the challenges through development of a two-stage coal processing. The technology is applicable to any coal, although Power River Basin (PRB) coal is used as an example feedstock in this research. In the 1st stage or pyrolysis process of the low-carbon-footprint technology, a Na-Fe bimetallic catalyst was found to be able to not only enhance the yield of CO and ratio of H2/CO but also lower CH4 and CO2 yields with the presences of the Na-Fe catalyst, which are desired because the produced gas is an ideal syngas. In the 2nd stage or gasification of the char obtained from pyrolysis stage with CO2 for producing almost 100%-purity CO without presence of H2O. The CO2 as the major byproduct of the 1st stage could be used as a raw material in the 2nd stage, which is an ideal process integration for significant reduction in CO2 emission. Also, the Na-Fe catalyst can accelerate not only the reaction kinetics in both stages but also increase the H¬2/CO ratio in the syngas produced in the 2nd stage. In other words, the catalyst is a multifunctional agent, which can not only intensify the overall coal process efficiency but also improve the qualities of the products and reduce CO2 emission.