Carbonation Reaction of Lithium Hydroxide during Low Temperature Thermal Energy Storage Process

In order to apply lithium hydroxide(LiOH)as a low temperature chemical heat storage material,the carbonation reaction of LiOH and the prevention method are focused in this research.The carbonation of raw LiOH at storage and hydration condition is experimentally investigated.The results show that the carbonation reaction of LiOH with carbon dioxide(CO_(2))is confirmed during the hydration reaction.The carbonation of LiOH can be easily carried out with CO_(2) at room temperature and humidity.LiOH can be carbonated at a humidity range of 10%to 20%,a normal humidity region that air can easily be reached.Furthermore,the carbonation reaction rate has not nearly affected by the increase of reaction temperature.An improved storage method by storing LiOH at a low humidity less than 1.0%can be effectively prevented the carbonation of LiOH.The hydration reaction ratio of LiOH at the improved storage method shows a better result compared to the ordinary storage method.Therefore,the humidity should be carefully controlled during the storage of LiOH before hydration and dehydration reaction when apply LiOH as a low heat chemical storage material.

Advanced In Situ Characterization Techniques for Direct Observation of Gas-Involved Electrochemical Reactions

Gas-involved electrochemical reactions provide feasible solutions to the worldwide energy crisis and environmental pollution.It has been recognized that various elements of the reaction system,including catalysts,intermediates,and products,will undergo real-time variations during the reaction process,which are of significant meaning to the in-depth understanding of reaction mechanisms,material structure,and active sites.As judicious tools for real-time monitoring of the changes in these complex elements,in situ techniques have been exposed to the spotlight in recent years.This review aims to highlight significant progress of various advanced in situ characterization techniques,such as in situ X-ray based technologies,in situ spectrum technologies,and in situ scanning probe technologies,that enhance our understanding of heterogeneous electrocatalytic carbon dioxide reduction reaction,nitrogen reduction reaction,and hydrogen evolution reaction.We provide a summary of recent advances in the development and applications of these in situ characterization techniques,from the working principle and detection modes to detailed applications in different reactions,along with key questions that need to be addressed.Finally,in view of the unique application and limitation of different in situ characterization techniques,we conclude by putting forward some insights and perspectives on the development direction and emerging combinations in the future.

Theoretical investigations on CO oxidation reaction catalyzed by gold nanoparticles

It is crucial to understand the mechanism of low temperature CO oxidation reaction catalyzed by gold nanoparticles so as to find out the origin of the high catalytic reactivity and extend the indus‐trialization applications of nano gold catalysts. In this work, some theoretical works on CO adsorp‐tion, O2 adsorption, atomic oxygen adsorption, formation of surface gold oxide films, reaction mechanisms of CO oxidation involving O2 reaction with CO and O2 dissociation before reacting with CO on gold surfaces and Au/metal oxide were summarized, and the influences of coordination number, charge transfer and relativity of gold on CO oxidation reaction were briefly reviewed. It was found that CO reaction mechanism depended on the systems with or without oxide and the strong relativistic effects might play an important role in CO oxidation reaction on gold catalysts. In particular, the relativistic effects are related to the unique behaviors of CO adsorption, O adsorption, O2 activation on gold surfaces, effects of coordination number and the wide gap between the chem‐ical inertness of bulk gold and high catalytic activity of nano gold. The present work helps us to understand the CO oxidation reaction mechanism on gold catalysts and the influence of relativistic effects on gold catalysis.

Single atom Cu-N-C catalysts for the electro-reduction of CO_(2) to CO assessed by rotating ring-disc electrode

The electrochemical CO_(2) reduction reaction(CO_(2)RR) to controllable chemicals is considered as a promising pathway to store intermittent renewable energy. Herein, a set of catalysts based on copper-nitrogendoped carbon xerogel(Cu-N-C) are successfully developed varying the copper amount and the nature of the copper precursor, for the efficient CO_(2)RR. The electrocatalytic performance of Cu-N-C materials is assessed by a rotating ring-disc electrode(RRDE), technique still rarely explored for CO_(2)RR. For comparison, products are also characterized by online gas chromatography in a H-cell. The as-synthesized Cu-NC catalysts are found to be active and highly CO selective at low overpotentials(from -0.6 to -0.8 V vs.RHE) in 0.1 M KHCO_(3), while H_(2) from the competitive water reduction appears at larger overpotentials(-0.9 V vs. RHE). The optimum copper acetate-derived catalyst containing Cu-N_(4) moieties exhibits a CO_(2)-to-CO turnover frequency of 997 h^(-1) at -0.9 V vs. RHE with a H_(2)/CO ratio of 1.8. These results demonstrate that RRDE configuration can be used as a feasible approach for identifying electrolysis products from CO_(2)RR.

Fundamental aspects in CO_(2) electroreduction reaction and solutions from in situ vibrational spectroscopies

Using renewable energy to drive carbon dioxide reduction reaction(CO_(2)RR)electrochemically into chemicals with high energy density is an efficient way to achieve carbon neutrality,where the effective utilization of CO_(2) and the storage of renewable energy are realized.The reactivity and selectivity of CO_(2)RR depend on the structure and composition of the catalyst,applied potential,electrolyte,and pH of the solution.Besides,multiple electron and proton transfer steps are involved in CO_(2)RR,making the reaction pathways even more complicated.In pursuit of molecular-level insights into the CO_(2)RR processes,in situ vibrational methods including infrared,Raman and sum frequency generation spectroscopies have been deployed to monitor the dynamic evolution of catalyst structure,to identify reactive intermediates as well as to investigate the effect of local reaction environment on CO_(2)RR performance.This review summarizes key findings from recent electrochemical vibrational spectrosopic studies of CO_(2)RR in addressing the following issues:the CO_(2)RR mechanisms of different pathways,the role of surface-bound CO species,the compositional and structural effects of catalysts and electrolytes on CO_(2)RR activity and selectivity.Our perspectives on developing high sensitivity wide-frequency infrared spectroscopy,coupling different spectroelectrochemical methods and implementing operando vibrational spectroscopies to tackle the CO_(2)RR process in pilot reactors are offered at the end.

Transition metal-nitrogen sites for electrochemical carbon dioxide reduction reaction

Electrochemical CO2 reduction reaction(CO2RR)powered by renewable electricity has emerged as the most promising technique for CO2 conversion,making it possible to realize a carbon‐neutral cycle.Highly efficient,robust,and cost‐effective catalysts are highly demanded for the near‐future practical applications of CO2RR.Previous studies on atomically dispersed metal‐nitrogen(M‐Nx)sites constituted of earth abundant elements with maximum atom‐utilization efficiency have demonstrated their performance towards CO2RR.This review summarizes recent advances on a variety of M‐Nx sites‐containing transition metal‐centered macrocyclic complexes,metal organic frameworks,and M‐Nx‐doped carbon materials for efficient CO2RR,including both experimental and theoretical studies.The roles of metal centers,coordinated ligands,and conductive supports on the intrinsic activity and selectivity,together with the importance of reaction conditions for improved performance are discussed.The mechanisms of CO2RR over these M‐Nx‐containing materials are presented to provide useful guidance for the rational design of efficient catalysts towards CO2RR.

Influence of anode current density on carbon parasitic reactions during electrolysis

In the electro-deoxidation process,carbon parasitic reaction(CO_(3)^(2-)+4e–=C+3O^(2-))usually occurs when using carbon materials as the anode,which leads to increase of the carbon content in the final metal and decrease of the current efficiency of the process.The aim of this work is to reduce the negative effect of carbon parasitic reaction on the electrolysis process by adjusting anode current density.The results indicate that lower graphite anode area can achieve higher current density,which is helpful to increase the nucleation site of CO_(2) bubbles.Most of CO_(2) would be released from the anode instead of dissolution in the molten CaCl_(2) and reacting with O^(2-)to form CO_(3)^(2-),thus decreasing the carbon parasitic reaction of the process.Furthermore,the results of the compared experiments show that when the anode area decreases from 172.78 to 4.99 cm^(2),CO_(2) concentration in the released gases increases significantly,the carbon mass content in the final metal product decreased from 1.09%to 0.13%,and the current efficiency increased from 6.65%to 36.50%.This study determined a suitable anode current density range for reducing carbon parasitic reaction and provides a valuable reference for the selection of the anode in the electrolysis process.

Bio-inspired carbon electro-catalysts for the oxygen reduction reaction

We report the synthesis, characterisation and catalytic performance of two nature-inspired biomassderived electro-catalysts for the oxygen reduction reaction in fuel cells. The catalysts were prepared via pyrolysis of a real food waste（lobster shells） or by mimicking the composition of lobster shells using chitin and CaCO3 particles followed by acid washing. The simplified model of artificial lobster was prepared for better reproducibility. The calcium carbonate in both samples acts as a pore agent, creating increased surface area and pore volume, though considerably higher in artificial lobster samples due to the better homogeneity of the components. Various characterisation techniques revealed the presence of a considerable amount of hydroxyapatite left in the real lobster samples after acid washing and a low content of carbon（23%）, nitrogen and sulphur（〈1%）, limiting the surface area to 23 m^2/g, and consequently resulting in rather poor catalytic activity. However, artificial lobster samples, with a surface area of ≈200 m^2/g and a nitrogen doping of 2%, showed a promising onset potential, very similar to a commercially available platinum catalyst, with better methanol tolerance, though with lower stability in long time testing over 10,000 s.

Effective exposure of nitrogen heteroatoms in 3D porous graphene framework for oxygen reduction reaction and lithium–sulfur batteries

The introduction of nitrogen heteroatoms into carbon materials is a facile and efficient strategy to regulate their reactivities and facilitate their potential applications in energy conversion and storage. However,most of nitrogen heteroatoms are doped into the bulk phase of carbon without site selectivity, which significantly reduces the contacts of feedstocks with the active dopants in a conductive scaffold. Herein we proposed the chemical vapor deposition of a nitrogen-doped graphene skin on the 3D porous graphene framework and donated the carbon/carbon composite as surface N-doped grapheme（SNG）. In contrast with routine N-doped graphene framework（NGF） with bulk distribution of N heteroatoms, the SNG renders a high surface N content of 1.81 at%, enhanced electrical conductivity of 31 S cm^（-1）, a large surface area of 1531 m^2 g^（-1）, a low defect density with a low I_D/I_G ratio of 1.55 calculated from Raman spectrum, and a high oxidation peak of 532.7 ℃ in oxygen atmosphere. The selective distribution of N heteroatoms on the surface of SNG affords the effective exposure of active sites at the interfaces of the electrode/electrolyte, so that more N heteroatoms are able to contact with oxygen feedstocks in oxygen reduction reaction or serve as polysulfide anchoring sites to retard the shuttle of polysulfides in a lithium–sulfur battery. This work opens a fresh viewpoint on the manipulation of active site distribution in a conductive scaffolds for multi-electron redox reaction based energy conversion and storage.

The First Report of Thermochemical Sulfate Reduction Reaction in the Upper Paleozoic Carbonate Rocks of Southeastern Ordos Basin

Thermochemical sulfate reduction （TSR） is the reaction between anhydrite and petroleum fluids at elevated temperatures to produce H2S and CO2. TSR has been studied in many sedimentary basins such as China＇s Sichuan and Tarim basins because it has a profound impact on the commercial viability of petroleum resources, with HzS typically being undesirable.

Ball-milling MoS_2/carbon black hybrid material for catalyzing hydrogen evolution reaction in acidic medium

Replacing platinum for catalyzing hydrogen evolution reaction （HER） in acidic medium remains great chal- lenges. Herein, we prepared few-layered MoS2 by ball milling as an efficient catalyst for HER in acidic medium, The activity of as-prepared MoS2 had a strong dependence on the ball milling time, Furthermore, Ketjen Black EC 300J was added into the ball-milled MoS2 followed by a second ball milling, and the resultant MoS2/carbon black hybrid material showed a much higher HER activity than MoS2 and carbon black alone. The enhanced activity of the MoS2/carbon black hybrid material was attributed to the increased abundance of catalytic edge sites of MoS） and excellent electrical coupling to the underlving carbon network.

SYNTHESIS AND CARBON TRANSFER REACTIONS OF 12-DIMETHYL-3-ARYLSULFONYL (ARYL=p-TOLYL PHENYL)-△~2-IMIDAZOLINIUM IODIDE

As models of 5, 10-methenyl-tetrahydrofolate coenaymes imidazolinium salts 6a. b were synthesized and their carbon transfer reactions with several types of nucleophiles were studied.

PALLADIUM CATALYZED REACTION OF 3-TRIMETHYLSILYLPROPARGYLIC CARBONATES WITH DINUCLEOPHILES

Methyl 3-trimethylsilylpropargyl carbonate reacted with dinucleophiles under the catalysis of palladium(0) complex to give the corresponding desilylated annulation products.

Selective synthesis of carbon monoxide via formates in reverse water–gas shift reaction over alumina-supported gold catalyst

Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al2O3： three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al2O3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO2 and H2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al2O3.

Promoting effect of nitrogen doping on carbon nanotube-supported RuO2 applied in the electrocatalytic oxygen evolution reaction

RuO2 nanoparticles supported on multi-walled carbon nanotubes（CNTs） functionalized with oxygen（OCNTs） and nitrogen（NCNTs） were employed for the oxygen evolution reaction（OER） in 0.1 M KOH.The catalysts were synthesized by metal-organic chemical vapor deposition using ruthenium carbonyl（Ru3（CO）（12）） as Ru precursor. The obtained RuO2/OCNT and RuO2/NCNT composites were characterized using TEM, H2-TPR, XRD and XPS in order probe structure–activity correlations, particularly, the effect of the different surface functional groups on the electrochemical OER performance. The electrocatalytic activity and stability of the catalysts with mean RuO2 particle sizes of 13–14 nm was evaluated by linear sweep voltammetry, cyclic voltammetry, and chronopotentiometry, showing that the generation of nitrogen-containing functional groups on CNTs was beneficial for both OER activity and stability. In the presence of RuO2, carbon corrosion was found to be significantly less severe.

Production of Superoxide Ion with Carbon Gas-Diffusion-Electrode And Reaction of Superoxide Ion with Aromatic Halide

Superoxide ion O^-_2 is prepared in aprotic media by carbon gas-diffusion-electrode for the first time. The experimental results indicate that this electrode is superior to carbon plane-electrode in the reaction of O^-_2 with p-bromonitrobenzene. When the gas-diffussion-electrode is used, the yield of the product nitrophenol increases by 20%, and the selectivity of the reaction is nearly doubled as compared with the plane-electrode.

Dual atomic catalysts from COF-derived carbon for CO_(2)RR by suppressing HER through synergistic effects

The electrochemical carbon dioxide reduction reaction(CO_(2)RR)for highvalue-added products is a promising strategy to tackle excessive CO_(2) emissions.However,the activity of and selectivity for catalysts for CO_(2)RR still need to be improved because of the competing reaction(hydrogen evolution reaction).In this study,for the first time,we have demonstrated dual atomic catalytic sites for CO_(2)RR from a core-shell hybrid of the covalent-organic framework and the metal-organic framework.Due to abundant dual atomic sites(with CoN_(4)O and ZnN_(4) of 2.47 and 11.05 wt.%,respectively)on hollow carbon,the catalyst promoted catalysis of CO_(2)RR,with the highest Faradic efficiency for CO of 92.6%at-0.8 V and a turnover frequency value of 1370.24 h^(-1) at-1.0 V.More importantly,the activity and selectivity of the catalyst were well retained for 30 h.The theoretical calculation further revealed that CoN_(4)O was the main site for CO_(2)RR,and the activity of and selectivity for Zn sites were also improved because of the synergetic roles.

Carbon Dioxide Captured from Flue Gas by Modified Ca-based Sorbents in Fixed-bed Reactor at High Temperature

Four kinds of Ca-based sorbents were prepared by calcination and hydration reactions using different precursors： calcium hydroxide, calcium carbonate, calcium acetate monohydrate and calcium oxide. The CO2 absorption capacity of those sorbents was investigated in a fixed-bed reactor in the temperature range of 350-650 ℃. It was found that all of those sorbents showed higher capacity for CO2 absorption when the operating temperature higher than 450 ℃. The CaAc2-CaO sorbent showed the highest CO2 absorption capacity of 299 mg.g-1. The mor- phology of those sorbents was examined by scanning electron microscope （SEM）, and the changes of composition before and after carbonation were also determined by X-ray diffraction （XRD）. Results indicated that those sorbents have the similar chemical compositions and crystalline phases before carbonation reaction [mainly Ca（OH）2], and CaCO3 is the main component after carbonation reaction. The SEM morphology shows clearly that the sorbent pores were filled with reaction products after carbonation reaction, and became much denser than before. The N2 adsorption-desorption isotherms indicated that the CaAc2-CaO and CaCO3-CaO sorbents have higher specific surface area. lar2er oore volume and anoropriate pore size distribution than that of CaO-CaO and Ca（OH）2-CaO.

S-doped carbon aerogels/GO composites as oxygen reduction catalysts

Composites of carbon aerogel and graphite oxide（GO） were synthesized using a self-assembly method based on dispersive forces. Their surface was modified by treatment in hydrogen sulfide at 650 and800 ℃. The samples obtained were characterized by adsorption of nitrogen, TA-MS, XPS, potentiometric titration, and HRTEM and tested as catalysts for oxygen reduction reactions（ORR） in an alkaline medium.The synergistic effect of the composite（electrical conductivity, porosity and surface chemistry） leads to a good ORR catalytic activity. The onset potential for the composite of carbon aerogel heated at 800 ℃ is shifted to a more positive value and the number of electron transfer was 2e-at the potential 0.68 V versus RHE and it increased to 4e-with an increase in the negative values of the potential. An excellent tolerance to methanol crossover was also recorded.

Effect of carboxymethyl cellulose on dissolution kinetics of carboxymethyl cellulose-sodium carbonate two-component tablet

Sodium carbonate and carboxymethyl cellulose powders are compressed into two-component tablets with three mass ratios,97%:3%,95%:5% and 93%:7%.The dissolution tests for two-component tablets and reference pure sodium carbonate tablets are carried out at various temperatures.The dissolution process of each tablet is measured by electrical conductivity tracking method and the concentration of dissolved sodium carbonate is quanti fied with calibrated conductivity-concentration converting equation of sodium carbonate.The quanti fied dissolution data is fitted with both surface reaction model and diffusion layer model and the results clearly show that surface reaction model is suggested as the appropriate dissolution model for all measured tablets.Therefore,it is determined that carboxymethyl cellulose is a stable element to remain the dissolution mechanism of tablet unchanged.The dissolution rate constant quanti fied with surface reaction model presents that carboxymethyl cellulose-sodium carbonate two-component tablets obtain signi ficant higher dissolution rate constant than pure sodium carbonate tablet and higher proportion of carboxymethyl cellulose leads to apparent higher dissolution rate constant.The results prove for the usage of carboxymethyl cellulose in most practical applications at a relative low-level,the effect of carboxymethyl cellulose is effective and positive for two-component tablet to enhance the dissolution process and improve dissolution rate constant and this effect is speculated coming from its dynamic physical transforming process in water including dilation and conglutination.