Oxide Desorption Research Articles

Synthesizing LiFePO4 by phosphate & iron recovered from sludge-incinerated ash and Li extracted from concentrated brines

Phosphorus (P) recovered from sludge-incinerated ash (SIA) could be applied to synthesize highly added-value products (FePO4 and LiFePO4) with in situ Fe in SIA. Indeed, LiFePO4 is a future of rechargeable batteries, which makes lithium (Li) highly needed. Alternatively, Li could also be extracted from concentrated brines to face a potential crisis of Li depletion on lands. Based on H3PO4 and Fe3+ co-extracted from the acidic leachate of SIA by tributyl phosphate (TBP), FePO4 (31.2 wt% Fe, 17.6 wt% P and the molar ratio of Fe/P = 0.98) was easily formed only adjusting pH of the stripping solution to 1.6. Interestingly, the organic phase from the first-stage co-extraction process of Fe3+ and H3PO4 could be utilized for Li-extraction from salt-lake brine, based on the TBP-FeCl3-kerosene system, and a good performance (78.7%) of Li-extraction and separation factors (β) (186.0–217.4) were obtained. Furthermore, the compounds with Li-extraction are complex, possibly LiFeCl4∙2TBP, in which Li+ could be stripped to form Li2CO3 by 4.0 M HCl (with a stripping rate up to 83%). Besides, Li2CO3 could also be obtained from desalinated brine by adsorption with manganese oxide ion sieve (HMO) and desorption with HCl. In the two cases, almost pure Li2CO3 products were obtained, up to 99.7 and 99.5 wt% Li2CO3 respectively, after further purification and concentration. Finally, recovered FePO4 and extracted Li2CO3 were synthesized for producing LiFePO4 that had a similar electrochemical property (69.5 and 77.8 mAh/g of the initial discharge capacity) to those synthesized from commercial raw materials.

Gaseous Nitric Oxide As Probe Molecule for Fe-N-C ORR Electrocatalysts

Iron nitrogen carbon (Fe-N-C) electrocatalysts remain the most promising platinum group metal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs). Although significant progress has been made in recent years in improving both the ORR activity and stability of the Fe-N-C catalysts, further enhancement in the catalyst durability while maintaining the activity is imperative for the practical applications. One of the major factors that hinders the further enhancement of the catalysts is the lack of clear understanding of the nature of the active sites and density of the active sites in the Fe-N-C catalysts due to the complexity of the Fe-N-C catalysts’ composition and structure. Gaseous nitric oxide was proven to be a suitable probe molecule that can bond to Fe and impede the ORR of the Fe-N-C catalysts. In recent years, we have studied the effects of gas-phase adsorption and desorption of nitric oxide on the redox features and ORR activity on Fe-N-C catalysts synthesized by different methods. We have used various characterization tools to quantify the amount of nitric oxide adsorbed and to identify the adsorption sites and geometry, including electrochemical stripping, temperature programmed desorption, and in situ X-ray techniques. The corresponding results obtained will be summarized in this talk. The implication of these results on the nature of the ORR active sites of the Fe-N-C catalysts will be discussed.AcknowledgementsThis work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the auspices of the Electrocatalysis Consortium (ElectroCat 2.0). This work utilized the resources of the Advanced Photon Source, a U.S. DOE Office of Science user facility operated by Argonne National Laboratory for DOE Office. This work was partially authored by Argonne, a U.S. Department of Energy (DOE) Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357.

Degradation mechanisms of annealed GaAsPBi films grown by molecular beam epitaxy

GaAsPBi is a novel semiconductor that can broaden the bandgap range of III−V compounds, but its growth on GaAs(001) by molecular beam epitaxy is complicated by the presence of Bi. To avoid the nucleation of Bi droplets, the growth temperature must be low (<400°C), resulting in GaAsPBi films with poor photoluminescent yields. It is shown here that while post-growth annealing of GaAsPBi improves its optical quality, the GaAsPBi surface and the underlying GaAsPBi/GaAs interface undergo structural and chemical changes that limit the usefulness of annealing. Using synchrotron radiation-based spectromicroscopy, morphological and chemical changes on the surface are followed in situ, allowing the temperature limit to be estimated at ∼510°C. Beyond this, the GaAsPBi film degrades, first by the nucleation of interfacial dislocations at ∼520°C, then by the desorption of surface oxides at ∼580°C, and by congruent sublimation of the film itself at ∼670°C. The damages are spatially correlated and inhomogeneous, with areas above the dislocations being the preferential damage sites. These in situ observed events provide critical insights to the mechanisms and chronology of surface and interfacial degradation during high-temperature processing of GaAsPBi/GaAs structure, with implications for the process and device designs of heteroepitaxial III−V films prevalence in optoelectronics.

Molecular Beam Epitaxy of Twin-Free Bi2Se3 and Sb2Te3 on In2Se3/InP(111)B Virtual Substrates

Three-dimensional topological insulators (3D-TIs) are a new generation of materials with insulating bulk and exotic metallic surface states that facilitate a wide variety of ground-breaking applications. However, utilization of the surface channels is often hampered by the presence of crystal defects, such as antisites, vacancies, and twin domains. For terahertz device applications, twinning is shown to be highly deleterious. Previous attempts to reduce twins using technologically important InP(111) substrates have been promising, but have failed to completely suppress twin domains while preserving high structural quality. Here we report growth of twin-free molecular beam epitaxial Bi2Se3 and Sb2Te3 structures on ultra-thin In2Se3 layers formed by a novel selenium passivation technique during the oxide desorption of smooth, non-vicinal InP(111)B substrates, without the use of an indium source. The formation of un-twinned In2Se3 provides a favorable template to fully suppress twin domains in 3D-TIs, greatly broadening novel device applications in the terahertz regime.

Experimental solubility and thermodynamic modeling of nitric oxide absorption in low-viscosity DBU-based deep eutectic solvents

Developing absorbents with highly efficient nitric oxide (NO) absorption and desorption is very important for flue gas denitrification process. Toward this end, a class of DBU-based deep eutectic solvents (DESs) containing alkanones or azoles as functional HBDs for the capture of NO were synthesized in this work, with viscosities of only 7.71–45.57 mPa·s at 303.2 K. Solubilities of NO in these DESs were determined at temperatures from 303.2 to 333.2 K and pressures from zero to 1 bar. It was found that the absorbing abilities of the DESs increased with the increasing HBDs’ alkalinity. Impressively, these DBU-based DESs had remarkable larger absorption capacities than those reported DESs in the literature. According to the solubility curves of NO, chemical absorption was thought to occur accompanying with the physical one in the systems. Therefore, the reaction equilibrium thermodynamic model (RETM) was applied to model the experimental NO solubilities. The corresponding thermodynamic parameters for each system, such as the reaction equilibrium constant, Henry’s law constant, and the enthalpy change were also obtained to assess the NO absorption process in these DESs.

Oxide desorption process from InSb surface under Sb flux

In this work, the process of oxide removal from the InSb (001) surface was studied in situ by high-energy electron diffraction in vacuum and under an antimony flux. The dependence of the oxide thickness on the annealing temperature was obtained. It has been found that the antimony flux slows down the process of oxide removal due to the oxide formation reaction. The oxide removal process was described by a system of kinetic equations, the activation energy of oxide decomposition was determined Keywords: InSb, oxide, activation energy, desorption.

Engineering sodium‐decorated bifunctional Au‐Ti sites to boost molecular transfer for propene epoxidation with H2 and O2

AbstractRegulating the microenvironment of active sites is crucial to boost the performance of direct propene epoxidation with H2 and O2. Herein, the enhanced surface transfer of H2O2 intermediates was first achieved by sodium‐decorated Au‐Ti bifunctional active sites. Combined with multi‐techniques (e.g., operando UV–vis–NIR system, DFT studies and quantitative model calculations), it is found that the sodium‐decorated silanols (Si‐ONa species) on the TS‐1 support enhance the formation of Ti‐OOH intermediates by restraining H2O2 decomposition. In addition, sodium‐decorated silanols improves the desorption of propylene oxide, suppressing its ring‐opening and formation for the carbonaceous deposits. Moreover, the sodium‐decorated Au nanoparticles with smaller diameter and higher electron density further strengthen O2 adsorption and boost the H2O2 formation. This work not only provides fundamental understandings on the microenvironment of Au‐Ti bifunctional catalysts but also sheds new light on enhancing the performance by boosting the surface molecular transfer.

Liquid-solid phase separation-generated multifunctional light-weight modification layer of g-C3N4/carbon endowing 5 V cathode material graphite flakes with high capacity and cyclicability simultaneously

Nowadays metal oxide coatings become one of the dominant ways to suppress electrolyte decomposition and consequantly improve cyclicability of high-voltage cathode materials for high energy-density batteries. However electrochemically inert nature and relatively high density of the metal oxides inevitably reduce cathode capacities. Meanwhile weak interfacial binding may induce desorption of the metal oxides during charge/discharge cycling. Herein a new strategy of light-weight g-C3N4/carbon coordinative modification of 5 V cathode material graphite flakes (GF) for dual-ion batteries is provided with aim to maintain graphite capacity and enhance interfacial binding strength simultaneously. Liquid-solid phase separation is utilized to generate multifunctional unique structure of the modification layer consisting of ultrafine g-C3N4 particles embedded homogeneously in carbon matrix, endowing the modified GF with high capacity and cyclicability for anion PF6─ storage simultaneously. A capacity enhancement of ~11% (1 C) is realized compared with that of TiO2/carbon modified GF, demonstrating superiority of the light-weight modification. Meanwhile capacity retention reaches 87% after 1500 charge/discharge cycles (5 C), exhibiting excellent cyclicability. The liquid-solid phase separation is an efficient way to generate homogeneous mixtures. Furthermore, the strategy of light-weight g-C3N4/carbon modification may provide a general way to improve capacity and cyclicability of other high-voltage cathode materials simultaneously.

Design of CuCs-doped Ag-based catalyst for ethylene epoxidation

Our recent theoretical studies have screened out CuCs-doped Ag-based promising catalysts for ethylene epoxidation [ACS Catal. 11, 3371 (2021)]. The theoretical results were based on surface modeling, while in the actual reaction process Ag catalysts are particle shaped. In this work, we combine density functional theory (DFT), Wulff construction theory, and micro kinetic analysis to study the catalytic performance of Ag catalysts at the particle model. It demonstrates that the CuCs-doped Ag catalysts are superior to pure Ag catalysts in terms of selectivity and activity, which is further proved by experimental validation. The characterization analysis finds that both Cu and Cs dopant promote particle growth as well as particle dispersion, resulting in a grain boundary-rich Ag particle. Besides, CuCs also facilitate electrophilic atomic oxygen formation on catalyst surface, which is benefitial for ethylene oxide formation and desorption. Our work provides a case study for catalyst design by combining theory and experiment.

Oxygen Adsorption and Desorption Kinetics in CuO Nanowire Bundle Networks: Implications for MOx-Based Gas Sensors

Copper oxide (CuO) nanostructures have demonstrated a good chemiresistive response for the sensing of various gases. The precise sensing mechanisms of this material and, in particular, the kinetics of the response to gases and the sensor recovery remain much less investigated. For metal oxide (MOx) chemiresistive gas sensors, oxygen adsorption and desorption reactions on a material surface play a major role in the sensor kinetics, as most other gases react with oxygen on the sensor surface in order to provide the sensing signal, and nanoscale materials are known to achieve faster response. Here we investigate the oxygen adsorption and desorption kinetics on CuO nanowire bundle (NWB) networks by analyzing the electrical response and recovery curves of sensing devices exposed to oxygen. The observation of multiple time constants for the response and recovery curves led us to discuss the various potential mechanisms related to surface reaction kinetics and diffusion of oxygen species. By comparing the reaction rate constants and diffusion constants extracted from the obtained time constants, we conclude that the diffusion of oxygen defects into the material might be the main reason for the observed large time constants. Surprisingly, we observe that the sensor devices based on as-deposited materials show 4–16 times faster response and recovery as compared to devices after being annealed, depending on the temperature. By comparing this result with detailed characterization using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, we discuss the role of the junctions between nanostructures in the network and of the hydroxylated CuO surface to explain this result. Our investigation on the kinetics of adsorption and desorption of oxygen of CuO NWB provides a direct understanding of the general response of the sensor and will be useful in order to further understand and optimize these materials for the sensing of various gases.

Design of CuCs-doped Ag-based catalyst for ethylene epoxidation

Our recent theoretical studies have screened out CuCs-doped Ag-based as promising catalysts for ethylene epoxidation (ACS Catalysis, 2021, 3371-3383). The theoretical results were based on surface modeling, while in the actual reaction process Ag catalysts are particle shaped. In this work, we combine Density functional theory (DFT), Wulff construction theory, and microkinetic analysis to study the catalytic performance of Ag catalysts at the particle model. It demonstrates that the CuCs-doped Ag catalysts are superior to pure Ag catalysts in terms of selectivity and activity in ethylene oxide production, which is further proved by our experimental results. The characterization analysis finds that both Cu and Cs dopants promote particle growth as well as particle dispersion, resulting in a grain boundary-rich Ag particle. Besides, CuCs also facilitates electrophilic atomic oxygen formation on catalyst surface, which is benefit for ethylene oxide formation and desorption. Our work provides a case study of Ag-based catalyst design for ethylene epoxidation by combining theory and experiment.

Dissolved trace elements dynamics during a rich-CO2-water leakage in a near-surface carbonate freshwater aquifer

An experimental leak “simulation” was carried out at the Saint-Emilion experimental site (France). A volume of 200 L of CO2-rich water was injected into the shallow carbonated aquifer during low water table periods. One injection well and seven monitoring wells were equipped with either CO2 probes or multi-parameters probes to follow the plume.After the CO2-rich water injection, dissolved CO2 and electrical conductivity increased as the pH values decreased, highlighting the calcite dissolution. The calcite dissolution and desorption of iron oxides led to the migration of trace elements in the aqueous phase. As, V, Mo Cu, Ga, Co, Fe, and Cd showed a rapid increase in their concentrations. Mn, Sr, Li and Se showed the same evolution but with a temporal offset. The concentrations of some of these elements increased a second time several hours after the injection. Ba and Pb showed a major decrease immediately after injection, but Ba showed two peaks several hours after the injection. Zn and Si seemed to not be affected by the CO2 injection.Only As, Ba, and Se exceeded WHO/UE drinking water standards for a period of few hours. The global return to initial conditions was fast, showing the great resilience and the high buffering capacity of carbonate aquifers.

Insights on copper, manganese, and Nickel/ZSM-5 catalytic mechanisms for nitric oxides selective reduction with ammonia

The elucidation of the selective catalytic reduction mechanisms over state-of-the-art metal-promoted zeolites is essential for nitric oxides removal in automobile and stationary source applications. In this work, H/ZSM-5 catalysts modified with transition metals, including copper, manganese, and nickel, were prepared by using an incipient wetness impregnation method and were evaluated for the selective reduction of nitric oxides with ammonia. Results indicate that copper/ZSM-5 exhibits the highest catalytic activity, with > 90% nitric oxide conversion at a broad operation temperature window (221–445 °C). The nitric oxide conversion profiles of nickel/ZSM-5 shows two peaks that correspond to weak activity among the catalysts; the low-temperature peak (290 °C) was induced by nickel clusters dispersed on the ZSM-5 surface, while the high-temperature peak (460 °C) was assigned to the bulk nickel oxides. The size of granular nickel monoxide crystallites with an exposed (2 0 2) plane is 2–30 nm, as confirmed by Scanning electron microscopy, X-ray diffraction, and Transmission electron microscope measurements. Temperature-programmed reductions with hydrogen results testified that the copper and nickel cations, as the main species contributing to selective catalytic reduction, were reduced via Cu2+/Cu+→Cu0 and Ni2+→Ni0 for copper/ZSM-5 and nickel/ZSM-5, respectively, while for the manganese/ZSM-5, the Mn3+ species in manganese clusters were reduced to Mn2+ by hydrogen. Particularly, temperature-programmed desorption coupled with mass spectrometer (TPD-MS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were comprehensively used to reveal the relationship between zeolite structure and catalysts’ properties for improving selective catalytic reduction. These results confirm that the ammonia is adsorbed and activated on both Brønsted and Lewis acid sites. The nitrous oxide desorbs in two stages during nitric oxide-TPD-MS measurements, corresponding to the desorption of nitric oxide bounded to amorphous clusters and the nitric oxide strongly bounded to bulk metal oxides, respectively. The selective catalytic reduction process follows the L-H mechanism at low temperatures, in which nitric oxide and ammonia molecules were adsorbed and activated on the catalyst surface. The selective catalytic reduction rates reached the maximum value of 1.8 × 108 (218 °C), 6.4 × 107 (227 °C), and 3.9 × 107 s−1 (235 °C) for copper, manganese, and nickel /ZSM-5, respectively.

High-performance and long-term thermal management material of MIL-101Cr@GO

Here, we demonstrate a breathing-like passive thermal management material based on moisture adsorption and desorption of graphene oxide (GO) modified chromium (III) terephthalate metal organic framework (MIL-101Cr), which breaks the limitation of latent heat limitation of common phase change materials and is highly desirable for long-term heat dissipation of batteries and chips. Nanoscale MIL-101Cr (50–100 nm) in-situ grown on the surface of GO (MIL-101Cr@GO) were prepared using a simple hydrothermal reaction method. In which, the MIL-101Cr acts as moisture adsorbent thus enables us to realize efficient heat dissipation through its moisture adsorption and desorption; while the GO acts as the nucleating agent for the growth of MIL-101Cr thus increases the nucleation rate and reduces the grain size of MIL-101Cr. As a result, the MIL-101Cr@GO shows high specific surface area and pore volume than that of pristine MIL-101Cr, resulting in higher moisture adsorption capacity and adsorption rate. In particular, the thermal management material MG6 (composed of MIL-101Cr and 6 wt% GO) shows a high moisture adsorption capacity of 1.391 g g−1 (i.e., 1 g absorbent can absorb 1.391 g moisture), 35.44% higher than that of MIL-101Cr. The thermal management material MG6 achieves 9.0 °C temperature drop under 95% relative humidity for a ceramic heater with a heating power of 4 W (similar to a typical Li-ion battery), and keep at ∼43.2 °C for at least 2 h. In addition, the material MG6 can remain 95% moisture adsorption capacity after 144 h of continuous operation, showing good thermal management performance and stability.

Combining trace Pt with surface silylation to boost Au/uncalcined TS‐1 catalyzed propylene epoxidation with H2 and O2

AbstractModification of bifunctional Au‐Ti catalysts for direct epoxidation of propylene with H2 and O2 is of burgeoning interest for potential commercialization requirements with desirable overall catalytic performance. Herein, we report a strategy by combining the addition of trace Pt into Au particles to enhance hydroperoxide species formation with the surface silylation to promote propylene oxide (PO) desorption. The resultant catalyst, that is, silylated Au20Pt1/uncalcined TS‐1, gives rise to significantly enhanced propylene conversion of 11%, PO selectivity of 88%, and H2 efficiency of 41%. The underlying nature of the above enhanced performance is elucidated by multiple techniques, such as high‐angle annular dark‐field scanning transmission electron microscopy, X‐ray photoelectron spectroscopy, Fourier transform infrared spectra, and theoretical calculations. The insights revealed here, the synergy of Au‐Pt‐Ti triple active sites together with the surface silylation, could guide the rational design of Au‐Ti catalysts for propylene epoxidation to boost PO production.

The Dynamics of Tungsten in Soil: An Overview

The increasing use of tungsten in the production of green energy in the aerospace and military industries, and in many other hi-tech applications, may increase the content of this element in soil. This overview examines some aspects of the behavior of tungsten in soil, such as the importance of characteristics of soils in relation to bioavailability processes, the chemical approaches to evaluate tungsten mobility in the soil environment and the importance of adsorption and desorption processes. Tungsten behavior depends on soil properties of which the most important is soil pH, which determines the solubility and polymerization of tungstate ions and the characteristics of the adsorbing soil surfaces. During the adsorption and desorption of tungsten, iron, and aluminum oxides, and hydroxides play a key role as they are the most important adsorbing surfaces for tungsten. The behavior of tungsten compounds in the soil determines the transfer of this element in plants and therefore in the food chain. Despite the growing importance of tungsten in everyday life, environmental regulations concerning soil do not take this element into consideration. The purpose of this review is also to provide some basic information that could be useful when considering tungsten in environmental legislation.

Comparison of Thermal and Atomic-Hydrogen-Assisted Oxide Desorption Methods for Regrowth of GaSb-Based Cascade Diode Lasers

Comparison of Thermal and Atomic-Hydrogen-Assisted Oxide Desorption Methods for Regrowth of GaSb-Based Cascade Diode Lasers

NO Binding Energies to and Diffusion Barrier on Pd Obtained with Velocity-Resolved Kinetics.

We report nitric oxide (NO) desorption rates from Pd(111) and Pd(332) surfaces measured with velocity-resolved kinetics. The desorption rates at the surface temperatures from 620 to 800 K span more than 3 orders of magnitude, and competing processes, like dissociation, are absent. Applying transition state theory (TST) to model experimental data leads to the NO binding energy E0 = 1.766 ± 0.024 eV and diffusion barrier DT = 0.29 ± 0.11 eV on the (111) terrace and the stabilization energy for (110)-steps ΔEST = 0.060–0.030+0.015 eV. These parameters provide valuable benchmarks for theory.

Polarity-controlled AlN/Si templates by in situ oxide desorption for variably arrayed MOVPE-GaN nanowires

In this paper, we present a comprehensive study of position-defined Al-polar AlN nucleation on lithographically patterned Si(111) substrates as a method to obtain ordered Ga-polar GaN nanowire arrays, with possible application in future nanowire-based devices such as LEDs and photoelectrochemical water-splitting cells. In a hydrogen processing step, ex situ prepared oxide on pre-structured Si-pillars could be selectively removed. This enabled Al-polar AlN nucleation on the Si-pillar’s sidewalls during the following metal–organic vapor phase epitaxy, while dominant N-polar AlN layer growth was observed on the still oxidized Si(111) horizontal substrate surface neighboring the pillars. 100% of the Ga-polar GaN wires are emerging on the Al-polar AlN growth sites, thus selective area epitaxy without any mask material could be realized. To gain a precise understanding of the growth mechanisms, the attainable Ga-adatom collection area per NW was varied by changing the Si-pillars’ placement pattern. The wire length and diameter increase with extended pitch. At a constant pitch, the size of the wires is adjustable by variation of the Si-pillars’ diameter, therefore growth of GaN wires of controllable dimension and pitch could be attained. Additionally, parasitic NW growth was completely suppressed for any pitch < 3.5 µm, while an increased pitch resulted in additional parasitic growth. Based on these results a model was derived, which includes the site-controlled removal of the oxide, the thus achieved local polarity control of AlN growth, and the influence of the collection area of each NW with respect to their size, whereas the collection area could be set in the experiment by adjustment of the lithographically controlled pitch and growth-parameter dependent Ga-adatom diffusion length. The mask-less polarity- and site-controlled growth of NWs with a height of 5.3 µm ± 0,33 µm and a diameter of 800 nm ± 160 nm at a pitch of 2.5 µm could be attained. Hence, a deep understanding of the growth mechanisms and the geometrical control of polarity- and site-controlled GaN NWs could be achieved, forming the base for development of NW-based devices on a conductive AlN/Si-template.

Influence of Water on Nitrous Oxide Adsorption and Desorption on Coals

Oxygen-enriched coal-combustion flue gas geologic sequestration in unmineable coal seams is a promising option to mitigate gaseous pollutant emissions and recover coalbed methane (CH4). Water (H2O) always exists in practical coal seams and shows significant impact on fluid adsorption, desorption, diffusion, and flow behaviors. Thus, this study mainly addressed the influence of H2O on nitrous oxide (N2O) adsorption and desorption, a typical component that existed in oxygen-enriched coal-combustion flue gas, on different rank coals. Results indicate that the N2O adsorption equilibrium and kinetic behaviors within moist coals can be well-predicted using the Sips model and the simplified bidisperse kinetic model, respectively. The H2O dramatically hinders the adsorption and diffusion capability of N2O within coals, which is attributed to the fact that H2O molecules occupy pore channels, induce coal matrix swelling, and compete with N2O molecules for the same adsorption sites, particularly the oxygen-containing functional groups. The H2O impairs the physisorption and chemisorption of N2O on coals. Furthermore, the H2O enhances the chemical transformation among the four main nitrogen-containing species within coals, that is, pyridine-N, pyrrole/pyridone-N, quaternary-N, and oxide-N. Particularly, the abundant −H groups of H2O molecules inhibit the decomposition of pyrrole/pyridone-N and accelerate the transformation of pyridine-N, while −OH groups of H2O molecules promote the formation of oxide-N. To sum up, the practical N2O geologic sequestration should focus on the effects of in-situ H2O within coal reservoirs.