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Adsorbent injection into flue ducts is an effective technology for controlling gaseous pollutant in coal-fired power plants. This study proposed a new technique of injecting dechlorinater into flue duct for HCl removal in order to realize the wet flue gas desulfurization (WFGD) wastewater sequestration and upgrade the gypsum quality, known as the source dechlorination method. Four alkaline-based adsorbents of CaO, Ca(OH)2 + 5 % NaOH, ethanol-modified CaO, and NaHCO3 were developed and investigated in a pilot scale 6 kW coal-fired circulating fluidized bed (CFB) combustion system for capturing flue gas HCl. The physical and chemical properties of the adsorbents were characterized to explore the reaction mechanisms affected by the adsorbent size and its distribution, active component loading, micro-structure, morphology, and crystal structure. The influences of the injection amount, resident time and flue gas temperature on the HCl removal efficiency were carried out, the dechlorination mechanism of the ethanol-modified CaO were discussed. The distribution of flue gas chlorine species across the air pollutant control devices (APCD) were obtained. This study provides basis for developing the technology of injecting dechlorinater into flue gas for HCl removal.

An interfacial electric field and S–C bonds as well as their effects benefiting the regulation of the efficiency of electrons transfer for efficient photocatalytic reactions are deeply investigated and comprehended.

Selective hydrogenation with high efficiency under ambient conditions remains a long-standing challenge. Here, a yolk-shell nanostructured catalyst, PdAg@ZIF-8, featuring plasmonic PdAg nanocages encompassed by a metal-organic framework (MOF, namely, ZIF-8) shell, has been rationally fabricated. PdAg@ZIF-8 achieves selective (97.5%) hydrogenation of nitrostyrene to vinylaniline with complete conversion at ambient temperature under visible light irradiation. The photothermal effect of Ag, together with the substrate enrichment effect of the catalyst, improves the Pd activity. The near-field enhancement effect from plasmonic Ag and optimized Pd electronic state by Ag alloying promote selective adsorption of the -NO

The fabrication of intrinsic carbon defects is usually tangled with doping effects, and the identification of their unique roles in catalysis remains a tough task. Herein, a K

The poor stability of organic-inorganic hybrid perovskites hinders its commercial application, which motivates a need for greater theoretical insight into its binding mechanism. To date, the binding mode of organic cation and anion inside organic-inorganic hybrid perovskites is still unclear and even contradictory. Therefore, in this work based on density functional theory (DFT), the binding mechanism between organic cation and anion was systematically investigated through electronic structure analysis including an examination of the electronic localization function (ELF), electron density difference (EDD), reduced density gradient (RDG), and energy decomposition analysis (EDA). The binding strength is mainly determined by Coulomb effect and orbital polarization. Based on the above analysis, a novel 2D linear regression descriptor that E

Catalytic oxidation of NO and Hg

Density functional theory calculations were used to study the adsorption of NO on Nin cluster (n = 1, 2, 3 and 4) doped graphene with different graphene-based support (single vacancy, one nitrogen decorated, two nitrogen decorated and three nitrogen decorated). The adsorption configuration, adsorption energy, charge transfer, density of states of NO on Nin/graphene are thoroughly studied. In addition, the d-band center and Fermi softness have been performed to consider the support effect. It is found that the support effect has a significant effect on the adsorption characteristics of NO molecule, which depends on the electronic structure of graphene-based support. The electronic structure can be characterized by the Fermi softness of the catalyst. Ni atom plays a more and more obvious role in NO adsorption process, with the increase of the number of Ni atoms. The Fermi softness is a great descriptors for the adsorption activity of the Nin/graphene. This result can contribute to the systematic study of graphene catalysts supported on metal clusters.

Nitric oxide (NO) releasing from power plants has caused global concerns. Converting NO to NO2 by catalytic oxidation technology is a promising method for NO elimination. Adsorption characteristics of corresponding gases and mechanism of NO oxidation on the surface of (Fe,Co)/N-GN catalyst were systematically investigated via density functional theory calculation. The detailed reaction paths in mechanism of Eley-Rideal and Langmuir-Hinshelwood were studied respectively and the thermodynamic and kinetic analysis of each path were performed to further understand the impact of temperature on the chemical equilibrium constant and reaction rate constant. It was observed that NO can be easily oxidized to NO2 on the surface of (Fe,Co)/N-GN with the smallest energy barriers about 0.17 eV in E–R mechanism, but the oxidation of NO in boiler is more likely to take place in L-H mechanism due to lower desorption barrier of generated NO2. Besides, we found CO played a promoting role in removal of residual oxygen atom, and H2O and SO2 had little impact on reaction under 800 K. We hope this work can not only lay a foundation for theoretical study of NO oxidation, but also provide a guideline for NO elimination in the coal-fired power plants.

Nitric oxide (NO) has been recognized as a major air pollutant, and the emission of NO has been strictly regulated. The technology of selective catalytic reduction of NO with NH3 injection is mature and efficient, but it still has some obvious drawbacks such as ammonia slipping, secondary fine particulates formation, and equipment corrosion. Therefore, a directly catalytic reduction of NO without ammonia injection by monovacancy graphene-based single atom iron catalyst (Fe/MG) was proposed. The detailed reaction mechanism was investigated through density functional theory calculation. Based on thermodynamic and kinetic analysis, we concluded that Langmuir-Hinshelwood is the dominant reaction mechanism for NO reduction, and the activation energy is 0.81 eV which is lower than char edges. The catalytic reduction reaction of NO is exothermic and thermodynamically favorable. The temperature can accelerate the catalytic reduction of NO. Based on the thermodynamic and kinetic performances of Fe/MG in NO reduction, Fe/MG is suggested to be a novel catalyst for NO reduction without NH3. This theoretical research results can provide a new insight for NO removal and lay some foundations for subsequent experimental research.

Arsenic and lead released from coal-fired power plant have caused great damage to environment and human health, making it critical to remove arsenic and lead simultaneously. The adsorption characteristics of HTMs (As2O3, Pb0, PbO and PbCl2) on the surface of single atom iron adsorbents supported with graphene-based substrates (Fe/GS) were systematically investigated through density functional theory calculation. The magnetic properties, bonding mechanism, reaction temperature and competitive adsorption behaviors were all considered in this work. Results demonstrated that Fe/GS of single vacancy with three nitrogen atoms doping (Fe/SV-N3) shows the most excellent adsorption capacity for HTMs among four types of Fe/GS. The adsorption of HTMs on Fe/SV-N3 belongs to stable chemisorption, and the adsorption can take place spontaneously when the temperature is below 700 K. To compare with the previously studied Hg0 system, the competitive adsorption behaviors of Hg0 and HTMs on Fe/SV-N3 were studied through relative adsorption ratio, Fe/SV-N3 will preferentially adsorb Pb0 and PbO when Hg0 and HTMs occur simultaneously at the temperature range of 300–1000 K. Therefore, Fe/SV-N3 is suggested to be a potential new material for gas detection and simultaneous removal of pollutants from coal-fired power plants.

The high efficiency of organic–inorganic hybrid perovskites has attracted the attention of many scholars all over the world, the chemical formula of which is ABX3, where A is an organic cation, B is a metal cation, and X is a halogen ion. In addition, the micro-mechanism behind the efficient photoelectric conversion needs more in-depth exploration. Therefore, in this work, based on time-dependent density functional theory (TD-DFT), the electron transfer mechanism from the ground state to the first singlet excited state was systematically investigated by electron and hole analysis and an inter-fragment charge transfer amount method (IFCT). In this work, we optimized and analyzed 99 different perovskite cluster configurations, where A sites are CH3NH3+ (MA+), NH2CHNH2+ (FA+), CH3CH2NH3+ (EA+), NH2CHOH+ (JA+), NH3OH+ (BA+), N(CH3)4+ (DA+), CH3CH2CH2NH3+ (KB+), CH3CH2CH2CH2NH3+ (KC+), C3N2H5+ (RA+), CH(CH3)2+ (TA+), and CH3NH(CH3)2+ (UA+), B sites are Ge2+, Sn2+ and Pb2+, and X sites are Cl−, Br− and I−. According to the analysis of a series of perovskite clusters of the hole–electron distribution, the distribution is mainly concentrated on BX, and electrons and holes are respectively distributed on B and X sites. The exciton binding energy decreases when the metal element changes from Ge to Pb and the halogen element changes from Cl to I. A radar chart including the exciton binding energy, excited energy, amount of net charge transfer, electron and hole overlap index, distance between the centroid of holes and electrons, and the hole and electron separation index was proposed to intuitively describe the electron transmission characteristics of perovskites. Based on that, a comprehensive score index was innovatively proposed to evaluate the photoelectric property of perovskites, providing foundational guidance for the design of high-efficiency organic–inorganic hybrid perovskites.

An accurate prediction model of catalytic activity is crucial for both structure design and activity regulation of catalysts. Here, a kinetic activity model is developed to study the activity of single-atom catalysts (SACs) in catalytic oxidation of sulfur dioxide. Using the adsorption energy of the oxygen atom as a descriptor, the catalytic activities of 132 SACs were explored. Our results indicate the highest activity when the adsorption energy of oxygen equals -0.83 eV. In detail, single-atom Pd catalyst exhibits the best catalytic activity with an energy barrier of 0.60 eV. Most importantly, this work provides a new insight for developing a highly accurate and robust prediction model for catalytic activity.

Coal is the dominant energy source in China, and coal-fired power plant (CFPP) accounts for about half of coal consumption. However, air pollutant emissions from coal-fired power plants cause severe environmental and ecological problems. The most stringent regulations to limit air pollutant emissions from CFPP have been implemented in China since 2015. The ultra-low emission standards require that particulate matters (PMs) concentration from stack must not exceed 5 mg/Nm3. For exploring the emission characteristics of particulate matters and some trace elements, the field sampling test was carried out in a 660 MW ultra-low emission coal-fired power plant. It is equipped with low temperature economizer (LTE), electrostatic precipitators (ESP), wet flue gas desulfurization (WFGD), and wet electrostatic precipitator (WESP). The results showed that the mass removal efficiency of PM10 is about 80% in ESP and about 70% in WESP, in which most of them are PM2.5. The mass concentration removal efficiency of PM10 was 98.77% in ESP while that of PM2.5 is 98.58%. The mass concentration removal efficiency of PM10 was 63.43% in WESP while that of PM2.5 is 71.92%. At the same time, the trace elements on different particle sizes were analyzed. Manganese contents were found to be independent of the particle size. Cr, As and Pb are mainly enriched in the fine ash particles. In terms of the emission factors, Cr, As, Pb, and Mn are mainly in the fine particles.

The mechanochemical (MC) brominated fly ash is a cost-effective mercury removal adsorbent, in which unburned carbon (UBC) plays an important role. The MC bromination mechanism of UBC and its mercury removal mechanism were completely studied through the density functional theory (DFT) method. Various defects on zigzag and armchair edge models were constructed at the micro-scale to simulate the MC effect on UBC at the macro-scale. The results reveal that the intact surface of zigzag and armchair can be constructed into abundant defective structures by MC action. Compared with the complete surface, bromine is more favorable to bind on the defective surface, resulting in more and stronger C-Br covalent bonds and more active sites. These defective structures also have a promoting effect on mercury adsorption. For the bromine-embedded structure, although the appropriate defective structure accounts for less, it not only can promote the adsorption and oxidation of mercury by improving adsorption ability or decreasing the oxidation energy barrier but is also easier to generate. Due to defect types formed by MC interaction on the UBC surface are much more diverse and complex, this study provides the theoretical basis for further research.

Nitric oxide (NO) emitted from coal-fired power plants has raised global concerns. The catalytic oxidation of NO is a promising technology for NO removal. Due to its high selectivity and high catalytic activity, a single-atom iron catalyst supported on a single-vacancy (SV) graphene-based substrate (Fe/SV) may be a promising catalyst for NO oxidation. The adsorption characteristics and reaction mechanisms of NO and O2 on the surface of Fe/SV were systematically studied through density functional theory calculation. The detailed reaction paths under the Langmuir–Hinshelwood, Eley–Rideal and termolecular Eley–Rideal reaction mechanisms were investigated, and thermodynamic and kinetic analyses were performed to study the effect of reaction temperature on the reaction rate and equilibrium. It is found that there are six different reaction paths which can be divided into two reaction patterns, step-by-step and simultaneous. The minimum activation energy of NO oxidation is only 0.04 eV and Eley–Rideal seems to be the dominant reaction mechanism of NO oxidation in flue gas. The reaction temperature has an obvious promoting effect on the reaction rate and an inhibitory effect on the reaction equilibrium. We hope that this research can lay a foundation for further theoretical research on NO oxidation and provide a guideline for experimental investigation on NO oxidation.

The release of mercury (Hg) species from coal-fired power plants has attracted increasing concern, and the development of an efficient and economical method to control Hg species emission from such plants is urgently required. Activated carbon is a compelling sorbent for the elimination of mercury species from flue gas, but the adsorption mechanism of mercuric oxide clusters on carbonaceous materials is still unclear. Therefore, the adsorption characteristics of mercuric oxide clusters on activated carbon were investigated systematically utilizing density functional theory in this work. It was found that mercuric oxide clusters are chemically adsorbed on activated carbon, and that the pre-adsorption of SO2 on the activated carbon leads to complicated mercuric oxide cluster adsorption behavior due to an irregular distribution of the electrostatic potential on the surface of the carbonaceous material. Thermodynamic analysis indicated that the adsorption energy of SO2 on activated carbon is lower than that of mercuric oxide clusters in the temperature range 298.15–1000 K. Competitive adsorption analysis suggested that mercuric oxide clusters are at least 108.11 times more likely than SO2 to be adsorbed on activated carbon.

The release of mercury (Hg) species from coal-fired power plants has attracted increasing concern, and the development of an efficient and economical method to control Hg species emission from such plants is urgently required. Activated carbon is a compelling sorbent for the elimination of mercury species from flue gas, but the adsorption mechanism of mercuric oxide clusters on carbonaceous materials is still unclear. Therefore, the adsorption characteristics of mercuric oxide clusters on activated carbon were investigated systematically utilizing density functional theory in this work. It was found that mercuric oxide clusters are chemically adsorbed on activated carbon, and that the pre-adsorption of SO

To realize simultaneous removal of pollutants released from coal-fired power plants, we carried out a theoretical study on catalytic oxidation of NO and Hg0 on the surface of single-atom Pd/g-C3N4 catalyst (Pdsac/g-C3N4), because after NO and Hg0 are converted to NO2 and Hg2+, products can be well absorbed in WFGD by using higher water solubility. Detailed reaction patterns in the mechanisms of Eley-Rideal (E-R), Langmuir-Hinshelwood (L-H), and termolecular Eley-Rideal (TER) were involved in this calculation. We revealed characteristics of catalytic reactions in thermodynamics and kinetics, and it was found most reactions were favorable in thermodynamics, and part reaction paths can take place spontaneously and irreversibly. Kinetics analysis evidenced the chemical reaction rates were all very fast because of short half-lives of reactants and large reaction rate constants. Fitted Arrhenius formula suggested the lowest activation energies of NO and Hg0 oxidation were just 0.46 eV and 1.81 eV, and therefore we speculated that Pdsac/g-C3N4 catalyst should be a potential catalyst for catalytic oxidation of NO and Hg0.

As important parts of simultaneous removal of multiple pollutants in flue gas, catalytic oxidation of Hg0 and adsorption removal of SO3, Pb species and As2O3 on the surface of (Fe,Co)@N-GN catalyst were systematically investigated in this work, using density functional theory. As a result, we found (Fe,Co)@N-GN not only showed great performance on Hg0 oxidation, but also exhibited outstanding removal capacity for SO3, Pb species and As2O3 molecules. Besides, PDOS and EDD analysis were carried out and the result indicated that electron transfer and orbit hybridization played key roles in gas adsorption. In addition, thermodynamics analysis further evidenced (Fe,Co)@N-GN was a qualified sorbent under 550 K, and competitive analysis suggested that the adsorption order of pollution gas was determined by adsorption energy, rather than the volume fraction of corresponding gases in flue gas. We hoped this work can not only lay a foundation for theoretical investigation of Hg0 oxidation, but also provide an important guideline for simultaneous removal of multiple pollutants released from coal-fired power plants.

Water-desorption from lignite surface is an important issue in energy usage, however, corresponding researches are inadequate. Herein, in order to comprehensive understand the process of water-desorption from lignite surface, the interaction between water molecules and carboxyl group of lignite were investigated systematically from 298.15 K to 440 K, by using Car–Parrinello molecular dynamics (CPMD) method. The result indicated that in the key carboxyl group, the hydrogen site (H51) showed stronger adsorption capacity for water molecules than the oxygen site (O23) of the carboxyl group. Based on the statistical result, the water molecules adsorbed at H51 and O23 were considered as removed after 360 K. Vibration analysis was performed to acquire stretching frequencies of carboxyl group before and after water adsorption. The NBO analysis was used to study the reorientation of water molecules in a 0.14 ps trajectory when they replace with each other. The NBO orbitals obtained show that when water molecule is replacing, the two lone pair orbitals of O31 and O32 interact with the σ antibonding orbital of O24 H51 bond at the same time. It enhances the formation of new H-bond and facilitates the fracture of old H-bond. This work can not only reveal the mechanism of water desorption from lignite, but also lay valuable foundations for efficient utilization of lignite resource.

The catalytic activation of O2 on nickel nanoclusters doped upon diff ;erent functionalized graphene substrates (monovacancy as well as one, two and three pyridinic nitrogen decorated) was investigated through the density functional theory calculation. We can observed the adsorption characteristics and the catalytic activation of O2 on catalysts is related to the support effect of diff ;erent functionalized graphene supports. The charge of Ni aotms has a good correlation with the adsorption energy of O2 on Nin clusters with different graphene-based support. The electron mainly transferred from the Ni clusters to the O2, and the graphene-based substrates plays a minor role in the electron transfer process. In addition, the Transition State Scaling are suitable for O2 dissociation reaction, and Transition State Scaling verify the accuracy of the O2 dissociation reaction calculation. Furthermore, in accordance with the energy barrier and the thermodynamic analysis of O2 activation reaction, the Ni3 clusters catalyst anchored single vacancy graphene decorated with three nitrogen atoms may be the most promising catalyst for O2 activation reaction. At the same time, this research will cast insight into activation reaction mechanism of O2 on metal nanoclusters catalysts and lay the foundation for the investigation of metal nanoclusters catalysts for the activation reaction of O2.