CO2 Gas Research Articles

Suspended nanophotonic waveguide for isotope-specific CO2 detection

The spectroscopic detection of gases and their stable isotopes holds significant value in bio-sciences and climate studies. However, achieving high precision has long been confined to bulky and costly equipment. In this work, we introduce a nanophotonic waveguide that is capable of detecting CO2 gas down to 20 parts per billion, and for the first time perform accurate stable isotope ratio measurements. The waveguide leverages a suspended membrane design with microstructured cladding, providing a high evanescent field confinement factor of 102%, moderate loss of 3.4 dB/cm, and effective suppression of etalons. The δ13C isotope ratio precision of 0.2‰ was achieved, replicating the performance of high-end laser absorption spectrometers. This marks the inaugural instance of on-chip, isotope-specific gas detection with a compact and cost-efficient system scalable to sensor networks.

Silver‐Based Supportless Membrane Electrode Assemblies for Electrochemical CO2 Reduction

ABSTRACTMost commonly, electrochemical CO2 reduction is performed in a three‐compartment setup employing gas diffusion electrodes (GDEs) to decrease mass transport limitations of the gaseous reactant CO2 to the reaction interface. However recently, there has been a rising number of investigations on suitable membrane electrode assemblies (MEAs) to overcome ohmic potential losses caused by the electrolyte gaps in the systems. While the significant majority of MEAs exhibited in literature is based on catalyst‐coated gas diffusion layers, this work presents an approach that does not require a likewise support. On the basis of a catalyst suspension similar to mixtures already employed for GDE production on industrial level, a method to directly transfer the resulting catalyst layers to the membrane is developed. The Faradaic efficiency of carbon monoxide, i.e. target product formation of GDEs manufactured according to a similar procedure, can be matched or even exceeded for individual modifications of the exchange MEAs. Simultaneously, the cell potentials can be remarkably decreased in this setup. By gradual adaptation of the fabrication procedure, the influence of important manufacturing parameters is unraveled, also discussing the effect of hydrogen permeation through the membrane.

Reactive carbon capture using electrochemical reactors.

The electrolytic upgrading of CO2 presents a promising strategy to mitigate global CO2 emissions while generating valuable carbon-based products such as carbon monoxide, formate, and ethylene. However, the adoption of industrial-scale CO2 electrolyzers is hindered by the high energy and capital costs associated with the purification and pressurization of captured CO2 prior to electrolysis. One promising solution is "reactive carbon capture," which involves the electrolytic conversion of the eluent from CO2 capture units, or the "reactive carbon solution," directly into valuable products. This approach circumvents the energy-intensive processes required for electrolyzers fed with gaseous CO2. This Tutorial Review highlights recent advances for reactive carbon capture, showcasing its potential as a scalable solution for electrolyzers that upgrade CO2 into fuels and products.

CALCULATION OF THERMODYNAMIC TEMPERATURES OF CHEMICAL REACTIONS OF STEPWISE MANGANESE REDUCTION PROCESS FROM ITS DIOXIDE BY CO GAS AND GASIFICATION OF SOLID CARBON BY DEGREES OF CHEMICAL AFFINITY OF SUBSTANCES TO OXYGEN

The results of a thermodynamic analysis of the course of chemical reactions of the stepwise reduction of manganese from its dioxide by CO gas and the gasification reaction of solid carbon (Bella-Boudoir) are presented. The goals of the work are to obtain eigenexpressions for calculating the numerical values of the Gibbs free energy depending on temperature using tabulated values of the standard enthalpies of formation and entropies of inorganic substances, as well as to construct graphical dependences of the Gibbs energy on temperature using formulas from literary sources and obtained expressions. Numerical values of the boundary temperatures are obtained above which the chemical reactions of the stepwise reduction of manganese from its dioxide by CO gas and the chemical reaction of gasification of solid carbon (Bella-Boudoir) can or cannot thermodynamically proceed. Considering the complete coincidence of the obtained data on the own (obtained) expressions using two (direct and indirect) methods, it is possible to consider with a significant degree of probability the numerical values of the boundary temperature for the reactions of stepwise reduction of manganese from its dioxide and gasification of solid carbon as reliable, which indicates the possibility of the reduction of Mn2O3 from MnO2, Mn3O4 from Mn2O3 and MnO from Mn3O4 by CO gas, the Bell-Boudoir reaction and the impossibility of the reduction of manganese from MnO by CO gas at the temperatures of the actual process in reduction furnaces. This also confirms that CO gas is not a manganese reducer at the last stage of stepwise reduction of MnO according to scheme (B), refuting any theories and assumptions about the possibility of reducing Mn from MnO by CO gas.

Hydrangea inspired hierarchical polyphosphazenes/molybdenum diselenide flame retardant as efficient enhancer for epoxy resin

The extensive use of epoxy resin (EP) is hindered by its high fire risk, particularly due to the significant heat release and emission of toxic substances during combustion. The utilization of organic flame retardant is plagued by its high dosage and subsequent deterioration in mechanical property of polymers. Hence, the integration of polyphosphazenes (PZS) and molybdenum diselenide (MoSe2) was conducted to acquire the hybridized flame retardants of PZS-Mo-A and PZS-Mo-B. With the additions of 3.0 wt% PZS-Mo-A and PZS-Mo-B, the reductions in PHRR reach 31.0 % and 33.0 %, while the decreases in total smoke production (TSP) are 13.4 % and 29.0 %. Moreover, the emission of toxic CO gas is impeded efficiently. This study provides promising prospects for the development of MoSe2-based hierarchical flame retardants, potentially expanding their applications in polymer composite materials.

Research and design of multiple gas mixing system in modified atmosphere packaging

Despite the abundant production of fruits and vegetables in Xinjiang, there is an increasing trend in waste rates. Gas-controlled packaging techniques are employed post-harvest to enhance freshness and extend shelf life. However, the multi-gas mixing system at the core of this equipment often encounters challenges such as insufficient stability, limited precision, high costs, and inadequate intelligence. In this context, we have developed and designed a multi-gas mixing system for gas-conditioned packaging. The system integrates Internet of Things technology, uses a programmable controller as the core, proposes a ternary gas distribution model based on the ideal gas equation and Dalton’s law of partial pressures, and utilizes RS-485 bus, TCP/IP protocol, among others. This ensures communication between the equipment and data transmission with the cloud server while enabling remote control of the gas mixing and blending process via a mobile phone terminal. The system runs stably through testing, with the average relative deviations of CO2 and O2 gas concentrations being 0.86% and 0.72%, respectively. This fulfills the technical prerequisites for achieving a gas concentration precision of less than 1%, addressing challenges related to inadequate precision in gas blending, unstable performance, and limited visual representation. Moreover, it significantly reduces equipment costs and operational complexities while serving as a valuable reference for advancing multivariate gas mixing and blending technology in Xinjiang’s fruit and vegetable gas-conditioned packaging.

A Cone-Like TSV Structured ZnO NO2 Gas Sensor that is Produced Using Room-Temperature Laser Drilling and Radio-Frequency Sputtering

A typical through-silicon via (TSV) has vertical and high aspect ratio holes, making special equipment required to deposit the film on the vertical hole walls. This study used room-temperature laser drilling to fabricate a cone-like TSV structure so that no special process equipment was required. Radio-frequency sputtering was used to deposit SiNx, ITO, and ZnO films on the cone-like TSV structure to form a ZnO NO2 gas sensor. Scanning electron microscopy and focused ion beam results show that the ZnO film connects the front and back sides of the substrate, enabling sensing on both sides. If the concentration of NO2 gas is increased, the sensor response increases and the average sensor response is 34,7%, with an inaccuracy of <± 1% for five 5 consecutive measurements using a NO2 concentration of 3ppm. Reactions with NH3, CO, CO2, and SO2 gases are almost insignificant, giving the cone-like TSV structure ZnO gas sensor good selectivity, stability, and reproducibility for NO2 gas.

Study on the gas composition of hydrate phase and unreacted liquid phase for hydrate-based gas separation

Hydrate-based gas separation (HBGS) method is an environment-friendly gas separation technique. At the end of the hydrate formation stage, the system usually consists of gas phase, hydrate phase and residual unreacted liquid phase. The separation efficiency of HBGS is usually determined by measuring the gas composition of gas phase before and after hydrate formation. It is currently unclear the gas composition of hydrate phase and residual unreacted liquid phase, and how they will affect the gas separation efficiency of HBGS separately. This work developed a novel method for efficiently separating the hydrate phase and the unreacted liquid phase, making it possible to directly measure the gas composition in the hydrate phase and residual unreacted liquid phase for the gas mixture hydrate system. The influence factors, such as operation conditions, gas composition of feed gas and types of guest gas on the gas composition of liquid and hydrate phases were studied. The experimental results show the mole fraction of CO2 in both hydrate phase and liquid phase are higher than that in the feed gas. The increase of system pressure and the mole fraction of CO2 in feed gas will obviously lead to the increase of the mole fraction of CO2 in hydrate phase, while slightly affect the mole fraction of CO2 in the liquid phase. When the mole fraction of CO2 in feed gas exceeds 80 %, the mole fraction of CO2 in the water phase will reach over 96 %, resulting in other influence factors being negligible. The mole fraction of N2 in hydrate phase is higher than that of H2, while the mole fraction of N2 in water phase is close to H2.

Experimental investigation on enhancing oil recovery of volcanic fractured oil reservoir by gas injection huff-n-puff considering gas diffusion

The pore structure of volcanic fractured oil reservoirs is complicated, and the traditional gas displacement and waterflooding are not ideal. In this paper, the pore structure characteristics of volcanic rock were analyzed. Then, the diffusion procedure of CO2 and natural gas in saturated oil porous media was analyzed by pressure drop method. Finally, huff-n-puff experiments of CO2 and natural gas were conducted to analyze factors on the recovery factor (RF), and the oil mobilization pattern was quantitatively characterized. By huff-n-puff, we mean injecting gas from one end and then soaking it for a period of time before producing oil, utilizing pressure-driven and physicochemical reactions to affect the oil. The results show that the pore size distribution range is large. The diffusion of CO2 and natural gas can be divided into three stages: rapid diffusion, slow diffusion and equilibrium, and the diffusion coefficient of CO2 is 10 times that of natural gas under same condition. Compared with vertical fractures and horizontal fractures, reticulate fractures have more influence on gas diffusion coefficient. After 6 cycles, the RF of CO2 is 15% higher than that of natural gas, and the contribution of the first 4 cycles to the RF is 91.38%. In addition, CO2 huff-n-puff primarily mobilizes oil in medium (0.1 μm < r < 1 μm) and large (r > 1 μm) pores. These research results can provide a good theoretical guidance for the efficient development of VFOR and CO2 sequestration.

Comprehensive overview of detection mechanisms for toxic gases based on surface acoustic wave technology

Identification and detection of toxic/explosive environmental gases are of paramount importance to various sectors such as oil/gas industries, defense, industrial processing, and civilian security. Surface acoustic wave (SAW)-based gas sensors have recently gained significant attention, owing to their desirable sensitivity, fast response/recovery time, wireless capabilities, and reliability. For detecting various types of targeted gases, SAW sensors with different device structures and sensitive materials have been developed with diversified working mechanisms. This paper is focused on overviewing recent advances in working mechanisms and theories of dominant sensitive materials and key mechanisms/principles for targeting various gases in the realm of SAW gas sensors. The basic sensing theories and parameters of SAW gas sensors are briefly discussed, and then the major influencing factors are systematically reviewed, including the effects of various sensitive layer materials, temperature/humidity, and UV illumination on the overall performance of SAW gas sensors. We further highlight the relationships and adsorption/desorption principles between sensing materials and key targeted gases, including NH3, NO2, H2S, explosive gases of H2, and 2,4,6-trinitrotoluene, and organic gases of isopropanol, ethanol, and acetone, as well as others gases of CO, SO2, and HCl. Finally, we discuss key challenges and future outlooks in designing methodologies of sensing materials and enhancing the performance of SAW gas sensors, offering fundamental guidance for developing SAW gas sensors with good sensing performance.

Experimental and kinetic study of pressurized CO2 gasification of biomass chars

Pressurized CO2 gasification of biomass represents an effective approach for the utilization of biomass and the reduction of CO2 emissions. The impact of CO2 partial pressure on the gasification kinetics of biomass chars was examined on a pressurized thermogravimetric analyzer at temperatures between 750 and 950 °C and elevated pressures (up to 1MPa). The findings demonstrated that the gasification rates of corn stalk char (CSC), toonasinesis sawdust char (TSC), and rice husk char (RHC) exhibited an increase with rising CO2 partial pressure. The reaction order exhibited variability with respect to CO2 partial pressure, gasification temperature, and biomass type. The reaction order associated with biomass char exhibited a higher value at the elevated CO2 partial pressure range (0.25–1.0MPa) relative to the low CO2 partial pressure range (0.025–0.1MPa). The nth-order model was employed to elucidate the gasification behaviors of biomass chars. The results indicated that the modified random pore model was successfully applied to model the gasification of CSC and TSC. The grain model was effective in predicting the gasification behavior of RHC. The gasification rates of the three biomass chars were accurately predicted by the Langmuir-Hinshelwood model at both low and high CO2 partial pressures. This study presents information on the effect of CO2 partial pressure on biomass char gasification and methods for predicting biomass char gasification under pressurized conditions.

The improvement on the properties and heavy metal solidification of phosphogypsum-steel slag cementitious material: Enhancement from Bi-directional carbonation

Despite the carbonation curing methods have been applied in many building materials, the low efficiency in solid waste utilization is still a big issue for applying this technique. Therefore, bi-direction carbonation curing was proposed and its performance, especially for the improvement in solidification/stabilization of heavy metal (Pb2+ and Cr3+), in phosphogypsum-steel slag cementitious materials (PSSC) was determined. In this study, PSSC with phosphogypsum (PG) and three kinds of steel slag (SS) with different fineness were prepared, and the bi-directional curing was achieved by mixing with Na2CO3 powder as the internal carbon source and curing under CO2 gas as the external carbon source. In addition to determining its effect on solidification efficiency, comprehensive strength, including X-ray diffraction, thermogravimetric analysis, and pore structure analysis were employed to reveal the changes in microstructure during carbonation after the addition of Na2CO3, and reveal the mechanism of PG on the hydration-carbonation of steel slag. The results showed the early-stage performance of PSSC was significantly improved and the solidification/stabilization performance for heavy metals was enhanced. The addition of Na2CO3 as an internal carbon source accelerates the time of carbonation curing, leading to higher early-stage strength of PSSC. By applying bi-directional carbonation curing, the solidification ability of PSSC with spatial structure denser for heavy metals Pb2+ and Cr3+ are improved by 80 % and 87 %, respectively, which could be attributed to the formation of nano-CaCO3 crystals.

Observing planetary gaps in the gas of debris disks

Recent ALMA observations discovered consequent amounts (i.e., up to a few 10−1 M⊙) of CO gas in debris disks that were expected to be gas-free. This gas is in general estimated to be mostly composed of CO, C, and O (i.e., H2-poor), unlike the gas present in protoplanetary disks (H2-rich). At this stage, the majority of planet formation already occurred, and giant planets might be evolving in these disks. While planets have been directly observed in debris disks (e.g., β Pictoris), their direct observations are challenging due to the weak luminosity of the planets. In this paper, with the help of hydrodynamical simulations (with FARGO3D) coupled with a radiative transfer code (RADMC-3D) and an observing tool (CASA), we show that planet-gas interactions can produce observable substructures in this late debris disk stage. While it is tricky to observe gaps in the CO emission of protoplanetary disks, the unique properties of the gaseous debris disks allow us to observe planetary gaps in the gas. Depending on the total mass of the gaseous debris disk, kinks can also be observed. We derive a simple criterion to estimate in which conditions gaps would be observable and apply it to the known gaseous debris disk surrounding HD 138813. In our framework, we find that planets as small as 0.5 MJ can produce observable gaps and investigate under which conditions (i.e., gas and planets characteristics) the substructure become observable with ALMA. The first observations of planet-gas interactions in debris disks can lead to a new way to indirectly detect exoplanets, reaching a population that could not be probed before, such as giant planets that are too cold to be detected by direct imaging.

SCExAO/CHARIS Near-infrared Scattered-light Imaging and Integral Field Spectropolarimetry of the AB Aurigae Protoplanetary System

We analyze near-infrared integral field spectropolarimetry of the AB Aurigae protoplanetary disk and protoplanet (AB Aur b), obtained with SCExAO/CHARIS in 22 wavelength channels covering the J, H, and K passbands (λ 0 = 1.1–2.4 μm) over angular separations of ρ ≈ 0.″13 to 1.″1 (∼20–175 au). Our images resolve spiral structures in the disk in each CHARIS channel. At the longest wavelengths, the data may reveal an extension of the western spiral seen in previous polarimetric data at ρ < 0.″3 out to larger distances clockwise from the protoplanet AB Aur b, coincident with the Atacama Large Millimeter/submillimeter Array–detected CO gas spiral. While AB Aur b is detectable in complementary total intensity data, it is a nondetection in polarized light at λ > 1.3 μm. While the observed disk color is extremely red across JHK, the disk has a blue intrinsic scattering color consistent with small dust grains. The disk’s polarization spectrum is redder than AB Aur b’s total intensity spectrum. The polarization fraction peaks at ∼0.6 along the major disk axis. Radiative transfer modeling of the CHARIS data shows that small, porous dust grains with a porosity of p = 0.6–0.8 better reproduce the scattered-light appearance of the disk than more compact spheres (p = 0.3), especially the polarization fraction. This work demonstrates the utility of integral field spectropolarimetry to characterize structures in protoplanetary disks and elucidate the properties of the disks’ dust.

Zr-MOF/MXene composite for enhanced photothermal catalytic CO2 reduction in atmospheric and industrial flue gas streams

In this study, a novel composite was engineered by integrating Zr-MOF (NH2-UIO-66) with MXene layers through electrostatic self-assembly. Under simulated sunlight and at 80 °C, this composite material achieved nearly complete conversion of low-concentration atmospheric CO2 to CO and CH4 without additional sacrificial agents or alkaline absorption liquids, marking one of the few reports demonstrating near-complete reduction of low-concentration CO2 directly from the air. For high-concentration CO2 in industrial flue gas, the composite utilized residual heat at 80 °C without additional energy input, exhibiting excellent CO2 reduction efficiency with CO and CH4 production rates of 127 μmol·g-1·h-1 and 330 μmol·g-1·h-1, respectively, resulting in a total production rate 4.76 times higher than that in the air. Compared to most reports on thermocatalytic CO2 reduction (>300 °C), this material shows significant advantages below 100 °C. The performance improvement is attributed to the introduction of Zr-MOF, which provides additional active sites and reduces activation energy. Additionally, the localized surface plasmon resonance (LSPR) effect of MXene facilitates the migration of thermal charge carriers to Zr4+ sites within the MOF. Density Functional Theory (DFT) calculations validate these findings. Overall, Zr-MOF/MXene composite holds potential for reducing CO2 in air and industrial settings, advancing energy conversion and environmental management.

Harnessing an adapted strain of Clostridium carboxidivorans to unlock hexanol production from carbon dioxide and hydrogen in elevated-pressure stirred tank reactors.

To successfully scale-up the production of bio-based building blocks through CO2 and H2-based gas fermentation, it is crucial to deeply understand and control the microbial catalyst response to the bioreactor environment. This study investigates the effects of key process parameters, such as CO2 and H2 partial pressures, gas feeding strategies, and mixture composition, on the production pathways of an evolved Clostridium carboxidivorans strain. The ultimate goal is to optimize 1-hexanol production in elevated-pressure stirred-tank reactors. Continuous gas feeding enhanced acetogenic and solventogenic metabolisms, while gas-limited conditions promoted chain elongation to caproic acid. An optimized process, combining an initial gas-limited step followed by a continuous gas phase, increased 1-hexanol production, achieving a maximum biomass-specific productivity of 0.9g gCDW-1 day-1. In-situ product extraction improved 1-hexanol carbon selectivity to an unprecedented 60%. These findings demonstrate the potential of CO2 and H2-fed fermentation to produce high-value chemicals other than ethanol and acetate.

Technical, economy and environmental assessment of an improved cooking stove: An experimental study

AbstractThis study assesses the technical, economic, and environmental assessment of a developed improved cookstove (ICS) for domestic uses focusing on outperforming the traditional charcoal cookstove by improving technical performance, fuel economy, and environmental savings. A set of experiments were conducted to verify the performance of the ICS. The technical performance involved measuring the cooking time (tc), maximum cooking temperature (Tmax), fuel consumption (fcons), thermal efficiency (ηth), and cooling time (tcool). The economic assessment involved daily and annual fuel cost, and daily and annual fuel cost saving while environmental saving involved annual reduction of CO, CO2, NO, and NOx gases. The Tmax of the ICS reached 1273 K, reducing the tc by 18 mins, a drop of 43%. Furthermore, this reduced the fcons by approximately 50 g, around 30%. The ICS had an enhanced tcool of about 24.53 mins and attained ηth of 43.3%. In five tests, the ICS consumed about 596 g, which costs TZS 870 and TZS 317,550 per year. The reduction in consumption significantly reduces fuel costs by 29.83%. The results showed the ICS reduced the emission of CO, CO2, NO, and NOx concentrations by 258, 650, 2, and 2.5 ppm, respectively, compared to a traditional charcoal cookstove.

Genotyping peculiarities of wheat photosynthesis light induction and productivity under the drought effect

Background. In agrocenoses, leaf light conditions are known to be unstable due to intermittent cloud cover and shading by other leaves or spikes. However, with a change in irradiance, photosynthesis does not reach its final value instantly, but with a certain delay. Due to this photosynthetic efficiency of leaves and crops is generally lower compared to stationary conditions. At the same time, the vast majority of works devoted to the problems of photosynthetic apparatus functioning under unstable light conditions do not take into account an adverse impact on photosynthesis of such a common stressor as drought. The aim of the present work was to study the peculiarities of flag leaves CO2 and H2O gas exchange parameters with changes in illumination under conditions of optimal and insufficient water supply in order to explore the pattern of drought effect on the photosynthetic induction processes in connection with productivity of wheat plants of different genotypes. Materials and Methods. The research was carried out on bread winter wheat varieties Yednist, Bohdana, Perlyna Podillia under conditions of pot experiment. Control plants were grown under an optimal soil moisture of 70 % field capacity (FC). In the experimental pots, soil drought was created at the level of 30 % FC for 7 days during the earing–flowering period, after that the soil moisture was restored to the optimal level. The parameters of flag leaf gas exchange were measured on the seventh day of drought. Components of plants grain productivity were determined after reaching full grain maturity. Results. It was found that according to the parameters of light induction curves of CO2 assimilation and transpiration, wheat plants of different genotypes under drought conditions are differentiated more clearly than under normal water supply. An increase in the limiting role of stomata in the induction of photosynthesis under drought conditions and changes in illumination was shown. Drought disrupts the coherence of stomatal conductance regulation in interaction with CO2 assimilation processes. This affects the light induction curves of photosynthesis and transpiration, and ultimately leads to a decrease in grain productivity. Conclusions. It was shown that in order to assess the efficiency of the photosynthetic apparatus in providing wheat plants with assimilates and maintaining their grain productivity under unfavorable conditions, the parameters of the response to the changes in illumination must be taken into account.

Impacts of Environmental Conditions on Thermal, Emissions and Economic Performance of Gas Turbine Using Different Types of Fuels: An Experimental Investigation

Gas turbine has been used widely for electrical power generation based on simple cycle system. However, the relatively low thermal efficiency engages the researchers in investigating possible methods to enhance gas turbine performance. In the current study, three different types of fuels were used (crude oil, light oil, and natural gas) to operate the gas power plant in Qayyara, Mosul, Iraq and to evaluate the plant's performance, environmental impact and economic cost. The Aspen Husys package was used for simulation based on data recorded by the control department. Results showed that the software applied was highly valid. The external environmental temperature influenced the performance and efficiency of the station significantly with maximum values obtained for winter by 114MW and thermal efficiency of 32.02% for natural. The emissions of CO2, SO2, and NOX gases are decreased, whereas CO emission is increased when the temperature of the external environment is raised with fewer emissions obtained for natural gas. The cost of three fuels in (summer) is the highest among the four months, with the higher cost for light fuel by 68.2 Iraqi diners/kiloWatt.hour. Therefore, light fuel cannot be used for the permanent operation of gas turbines, and natural gas fuel gives better performance and lower emissions than the other two types of fuels.

Graphite-enhanced methanogenesis in coal measure shale anaerobic digestion: Implications for increasing gas yield and CO2 utilization

Anaerobic digestion (AD) of coal measure shale (CMS) for methane production is a promising technology for increasing yield of coal measure gas (CMG) wells. However, improving methane production efficiency of CMS remains a challenge. Conductive material has been shown to promote biogas production in different AD systems, but its effectiveness in CMS requires investigation. In this study, graphite was selected as conductive material due to its low cost and suitability for field applications, and its effects on methane production was investigated. The results indicate that as graphite concentration increases from 0 to 1.6 g/L, the methane production of CMS increases. However, when the graphite concentration reaches 2.0 g/L, the methanogenesis is inhibited, resulting in lower methane production compared to the control group. In the group with a graphite concentration of 1.6 g/L, the abundances of Romboutsia and Pseudomonas increase, which improves the compatibility of the microbial community with the CMS AD system and causes the amount of the substrates for methanogenesis to increase. Also, the direct interspecies electron transfer between Methanobacterium, Methanosaeta and Pseudomonas is strengthened, which enhances the methane production. However, excessive addition of graphite (2.0 g/L) intensifies the competitions from dissimilatory iron reduction and sulfate reduction reactions for substrates and electrons with the methanogenesis, causing the methane production to decrease. This study confirms the effectiveness of graphite in enhancing methane production of CMS, and the promoted hydrogenotrophic methanogenesis enhances the CO2 methanation, which offers an efficient pathway for increasing CMG well yield and enabling CO2 underground utilization.