CO2 Decomposition Research Articles

Optimal design of PdAu/In2O3 catalysts for CO2 hydrogenation

Efficient catalyst design has garnered significant interest in recent decades due to its potential to address both the challenges of the greenhouse effect and energy shortages by facilitating the conversion of CO2 into valuable chemicals through catalytic reactions. To investigate maximizing the synergistic effects of supported PdAu catalysts, we conducted first-principles calculations on the activation and decomposition of CO2 and H2 on the PdAu/In2O3(110) system. The results demonstrate that the incorporation of a secondary metal (Au) into the supported Pd catalyst, in conjunction with precise control over Au concentration, exerts influence on both reactant binding energy and activation. The adsorption and activation of CO2 at the interface sites of Au4/In2O3(110) and PdAu3/In2O3(110) are not observed. The transition state for the dissociation of CO2 into *CO and *O is determined based on adsorbed CO2, providing insights into the properties of activated CO2. The Bronsted–Evans–Polanyi relation, which correlates activation barriers (Ea) with reaction energies (Er), was established for the CO2 dissociation mechanism on PdAu/In2O3(110) catalysts using equation E = 0.4Ea + 0.63. It was carried out to investigate the H2-dissociated adsorption processes and mobility energy on various PdAu/In2O3(110) catalysts. Finally, a highly efficient Pd2Au2/In2O3 catalyst for the hydrogenation of CO2 into methanol has been proposed. This research provides valuable insights into the hydrogenation of CO2 to methanol using bimetal-oxide catalysts and contributes to the optimization of the design of PdAu/In2O3 catalysts for CO2 reactions.

Enhancing CO2 conversion in a temperature-controlled DBD plasma reactor with HKUST-1 catalyst: Water removal and CuO/Cu2O-derived approach

Due to a synergy effect, using dielectric barrier discharge (DBD) plasma technology combined with catalysts for CO2 decomposition, a major contributor to global warming, is recognized as an effective approach to transforming CO2 into valuable products such as CO, which is a crucial feedstock for chemical synthesis. Herein, HKUST-1 was synthesized using the hydrothermal method for CO2 conversion in the DBD reactor. To enhance catalyst performance in the plasma region, HKUST-1 was treated with O2 plasma to increase its specific surface area. Additionally, HKUST-1 was calcined at 300 °C to produce the CuO/Cu2O catalyst. Since the recombination reaction in the CO2 conversion is increased at higher temperatures, the reactor heat is removed using fan cooling and a water circulation system. In the presence of the HKUST-1 catalyst, the CO2 conversion rate significantly increased by 132 %, 82 %, and 12 % in reactors operating without cooling, with fan cooling, and with water cooling circulation, respectively compared to the reactors without catalyst, at a flow rate of 50 ml/min and maximum input power. The catalysts have been characterized using a comprehensive suite of analytical techniques, including FTIR, XRD,TEM, SEM, EDS, and BET analysis. The BET analysis indicates that the specific surface area of HKUST-1 after O2 plasma treatment is increased by 52 %, which causes an increasing conversion rate of up to 18 %. The CuO/Cu2O catalyst demonstrated maximum CO2 conversion of 21 % at an input power of 140 W and achieved energy efficiency of 8.6 % at 40 W. The presence of oxygen vacancies within this catalyst enhances the process of CO2 decomposition.

Reactive molecular dynamics simulations of poly(vinyl alcohol) gasification in supercritical carbon dioxide

Supercritical fluid gasification technology, as an environmentally friendly technology, can convert organic components of plastic waste into fuels and chemical materials. Moreover, the utilization of CO2 as the gasification environment holds significant importance for reducing carbon emissions. To better comprehend the microscopic mechanism of plastic gasification in supercritical environment, this sthdy used the Reactive Force Field (ReaxFF) molecular dynamics method to study the gasification process of long-chain poly(vinyl alcohol) molecule in supercritical H2O/CO2 under different reaction conditions. The result illustrated that during the gasification process, poly(vinyl alcohol) initially depolymerized into multiple long carbon chain (C5+) molecular fragments. Subsequently, these fragments underwent cleavage into short carbon chains and various gaseous small molecules. In this reaction, O radicals generated by CO2 decomposition play a crucial role in promoting the cleavage of plastic C–C bonds. In addition, through the analysis of the products and chemical bonds, we found that increasing temperature and prolonging reaction time significantly enhance the gasification efficiency and hydrogen production of plastics. Conversely, exceedingly high pressure inhibits the gasification reaction.

Biphasic gas–liquid millifluidic system for carbon dioxide plasma chemistry: Application to controlled selective epoxidation

The integration of nonthermal CO2 plasma for olefin epoxidation within a biphasic gas–liquid millifluidic system is presented. In this innovative approach, CO2 is efficiently reduced to CO and O atoms, facilitating the epoxidation of olefins. Analysis of the system’s effluent shows that epoxide production efficiency and yields, optimized to 90 %, significantly surpass those of traditional plasma methods, attributed to the enhanced gas–liquid mass transfer within the millifluidic environment. Moreover, O atoms generated from CO2 decomposition was observed to travel up to 30 mm in the post-plasma discharge area, enhancing the gas–liquid flow system’s efficiency. By capturing O atoms in the epoxidation reaction with olefins, the reverse reaction with CO is minimized, which in turn, markedly increases CO yield under the same conditions without olefins. These findings demonstrate that olefin epoxidation can be activated through CO2 plasma discharge in a controlled, selective, and catalyst-free manner under gentle conditions. This synergy between nonthermal plasma and millifluidic technologies paves the way for overcoming current limitations in plasma chemistry with industrial relevance.

Plasma Catalysis-Driven Decomposition of CO2: Optimizing Energy Distribution with NiCo-CuO Catalyst

Plasma Catalysis-Driven Decomposition of CO₂: Optimizing Energy Distribution with NiCo-CuO Catalyst

Coproduction of metal oxide and CO2 through decomposition of carbonate in a moving bed with a central gas-flow channel

During carbonate calcination process, the block ores are often directly heated by high-temperature flue gas, which inevitably dilutes the potentially high-concentration CO2 from carbonate decomposition. In this study, we well implemented the coproduction of lightly burned magnesia (LBM) and high-concentration CO2 through decomposition of small-size magnesite in a devised novel moving bed reactor. The reactor is installed with a central gas-flow channel as internals to convert the moving bed into a radially flowing reactor, making it can process small-size particles. Verification of this design was implemented in an electrically heated pilot-scale facility processing about 10 kg h−1 magnesite (0–6 mm), and gaseous product contains about 99% CO2. Systematic tests employing laboratory fixed bed reactors with and without internals further showed that the thickness of particle layer between the heating wall and the central internals substantially affects heat transfer from outside to the inside, thus influencing the decomposition. It is particularly for magnesite because the formed LBM is both heat-resistant and flame-retardant. Therefore, an updated reactor for small-size carbonates decomposition and coproduction of CO2 is proposed.

Highly efficient dual-phase hydrogen-transporting membranes for NH3 decomposition coupling with CO2 reduction

Hydrogen-transporting membrane reactors play active roles in ammonia (NH3) decomposition and carbon dioxide (CO2) reduction by combining reaction and separation in one unit, simplifying the processes and reactor design and therefore saving the cost. These important reactions normally occur at high temperatures and in reducing and acidic atmosphere, thus posing great challenges on the membrane stability. Previous effort was devoted to thin Pd membranes, which however, suffer the shortcomings of hydrogen embrittlement, CO poisoning and high costs. Herein, we develop a H2-COx-tolerant and non-noble metal-ceramic dual-phase hydrogen permeable membrane reactors with a nominal composition of 60 vol% Ni-40 vol% La5.5WO11.25-δ (Ni-LWO). NH3 decomposition and hydrogen permeation was observed via the developed mixed protonic and electronic conducting membrane. A considerable production of CO in the sweep (CO2) side could also be achieved from CO2 reduction when the membrane was coupled by NH3 decomposition where the permeated hydrogen can consume the produced oxygen from favorable CO2 decomposition. Furthermore, we systematically investigated the performance of NiO–CeO2 catalyst coated Ni-LWO membrane reactor for CO2 reduction. Noteworthy that the CO generation rate obtained from Ni-LWO membrane reactor was increased in the presence of NiO–CeO2 catalysts. Hydrogen separation process coupled with surface reactions is jointly controlled by hydrogen surface exchange and bulk diffusion kinetics. These findings reveal a vital step towards the development of efficient hydrogen-transporting membrane reactor for the integration of chemical reactions and separation processes.

Investigation into the photothermal catalytic CO2 decomposition over CeO2 with different morphologies: Behaviors of oxygen vacancies

CO2 is a viable renewable energy source, as global CO2 emissions are perennially increasing. The decomposition of CO2 to CO and O2 through high-temperature cracking of metal oxides via a two-step thermochemical cycle has been an effective strategy to reduce CO2 concentrations in the atmosphere. However, this thermochemical cycle requires a high reaction temperature (1273 K). Hence, in this study, we investigated photothermal CO2 decomposition over three CeO2 catalysts with different morphologies: porous CeO2 nanosheets (2D-CeO2), cubic-shaped CeO2 (C-CeO2), and octahedral CeO2 (O-CeO2). The photothermal synergistic effect eliminated the necessity of high temperatures, where light illumination increased the generation of oxygen vacancies and electron transfer to promote CO2 decomposition. The maximum rate of CO production by 2D-CeO2 at 250 °C was 69 μmol g-1h−1, which is significantly higher than those of O-CeO2 (47 μmol g-1h−1) and C-CeO2 (19 μmol g-1h−1). However, no activity was observed in dark conditions, even at 250 °C. In-situ DRIFTS, quasi in-situ EPR, XPS, and Ar-TPD experiments revealed that light irradiation promotes the production of oxygen vacancies on the catalyst surface and generates the intermediate CO2•− species, which cleave the C=O bonds and CO2 conversion, while temperature promotes the adsorption of CO2 on the catalyst surface and facilitates electron transfer. DFT calculations revealed the differences in oxygen vacancy formation and CO2 adsorption among various exposed crystal facets of CeO2. These findings provide new avenues for CO2 decomposition based on the adsorption and activation of CO2 on metal oxide surfaces and the low-temperature synergistic photothermal effect.

A spray-on environmentally friendly degradable mulch material and its high efficiency in controlling above-ground biomass of weeds in greenhouse experiments

AbstractThis study describes a novel spray-on mulch material as an alternative to currently used weed control methods. The mulch material is based on renewable raw materials, mainly rapeseed oil, starch and sodium alginate.Laboratory tests were conducted to obtain a mulch material with the best possible properties. Formulations with different ingredients were prepared and tested for their material properties. The formulations were investigated for potential shrinkage tendency and heat resistance as well as water resistance. Further tests such as resistance to mould infestation and aerobic degradability according to DIN EN ISO 17556 were carried out with the formulation that performed best in the previous tests. Mould resistance was enhanced by adding sodium benzoate. In the laboratory experiment, the CO2 decomposition rate was about 30% after seven weeks. With the favouritised variant, which was found step by step through the experiments, an outdoor field test was carried out to investigate the durability under natural conditions over the vegetation period. In the field, the mulch material maintained its function for six months. In the greenhouse, the effect of the mulch material on weeds was studied. It was found that the mulch material showed a high efficiency in controlling above-ground biomass of Elymus repens, Amaranthus retroflexus, and Setaria viridis. In addition, the biomass of the roots of Amaranthus retroflexus and Elymus repens was reduced. Further studies are on the way to elucidate field suitability and the weed suppressive effect under different environmental conditions.

Tailored SrFeO3-δ for chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CL-DRM) is a highly efficient process that converts two major greenhouse gases (CH4 and CO2) into syngas ready for the feedstock of liquid fuel production. One of the major obstacles facing this technology now is creating oxygen carriers that are stable and reactive. We fabricated high-performance Sr0.98Fe0.7Co0.3O3-δ perovskite-structured oxygen carrier by combining A-site defects and B-site doping of SrFeO3-δ. During isothermal CL-DRM tests at 850 °C, Sr0.98Fe0.7Co0.3O3-δ achieved 87% CH4 conversion and 94% CO selectivity in the CH4 partial oxidation reaction, followed by a syngas yield of 8.5 mmol/g, and CO yield of 4.2 mmol/g in CO2 decomposition. A-site defect engineering of the perovskite creates abundant oxygen vacancies and enhances oxygen storage capacity (OSC). Co-doping of the B-site of Sr0.98FeO3-δ increases oxygen mobility and CH4/CO2 activation, resulting in high activity in the CL-DRM process. This methodology resulted in high ionic mobility and facilitated the rapid diffusion of oxygen in the bulk phase, thereby increasing the redox properties of SrFeO3-δ. The oxygen carrier exhibits excellent structural stability and regeneration ability in successive redox cycles. This strategy offers a simple but very effective pathway to tailor OSC, oxygen mobility, and oxygen vacancies of perovskite-structured materials for chemical looping or redox-involved processes.

Activating 2D MoS2 by loading 2D Cu–S nanoplatelets for improved visible light photocatalytic hydrogen evolution, drug degradation, and CO2 reduction

Finding reliable photocatalysts capable of driving reactions using only sunlight is more needed than ever. A variety of strategies to harvest sunlight and convert it into chemical energy have been successfully utilized such as synthesizing nanostructures, using metal nanoparticles, doping, and others. In this work, we discover a facile way to anchor CuS nanoplatelets on 2D MoS2 by the solvothermal method using ethylene glycol (EG) as both a reduction agent and an exfoliating agent of bulk MoS2. Using CuS as a co-catalysis on MoS2 with their huge surface areas, led to improved photocatalytic activity for three different applications including H2 evolution, CO2 reduction, and endosulfan degradation. Specifically, Cu–S@MoS2 3% nanocomposite produced 9.86 μmol g−1 h−1 of H2, 0.48 μmol g−1 h−1 of CO and full decomposition of endosulfan within 6 h. The Cu-loaded MoS2 nanocomposites were thoroughly characterized by spectroscopic (including synchrotron-based spectroscopy) and microscopic methods to understand the formation of Cu–S during the solvothermal process. Moreover, the role of the EG during the synthetic procedure was revealed experimentally and studied theoretically via DFT simulations.

Low-Overpotential Rechargeable Na-CO2 Batteries Enabled by an Oxygen-Vacancy-Rich Cobalt Oxide Catalyst.

Rechargeable sodium-carbon dioxide (Na-CO2) batteries have been proposed as a promising CO2 utilization technique, which could realize CO2 reduction and generate electricity at the same time. They suffer, however, from several daunting problems, including sluggish CO2 reduction and evolution kinetics, large polarization, and poor cycling stability. In this study, a rambutan-like Co3O4 hollow sphere catalyst with abundant oxygen vacancies was synthesized and employed as an air cathode for Na-CO2 batteries. Density functional theory calculations reveal that the abundant oxygen vacancies on Co3O4 possess superior CO2 binding capability, accelerating CO2 electroreduction, and thereby improving the discharge capacity. In addition, the oxygen vacancies also contribute to decrease the CO2 decomposition free energy barrier, which is beneficial for reducing the overpotential further and improving round-trip efficiency. Benefiting from the excellent catalytic ability of rambutan-like Co3O4 hollow spheres with abundant oxygen vacancies, the fabricated Na-CO2 batteries exhibit extraordinary electrochemical performance with a large discharge capacity of 8371.3 mA h g-1, a small overpotential of 1.53 V at a current density of 50 mA g-1, and good cycling stability over 85 cycles. These results provide new insights into the rational design of air cathode catalysts to accelerate practical applications of rechargeable Na-CO2 batteries and potentially Na-air batteries.

Genetic parameters for ewe lifetime productivity traits in Central Anatolian Merino sheep

Rapidly increasing population size, recent breaks in production and supply chains, due to pandemics, and those further expected because of climate change emphasize the compelling importance of animal productivity. Traits associated with the productivity of ewes have a direct impact on the overall productivity, profitability and efficiency of sheep farms. Therefore, the objective of the current study was to estimate the variance components, heritabilities as well as genetic and phenotypic correlations, for traits associated with the lifetime productivity of Central Anatolian Merino ewes. Birth and weaning records of lambs for each ewe as well as environmental factors such as sex and birth type were utilized for deriving ewe lifetime productivity traits. Genetic parameter estimations involved observations from 3101 Central Anatolian Merino ewes, encompassing mean and total lamb birth weight per ewe (MBW and TBW), mean and total lamb weaning weight per ewe (MWW and TWW), and the mean and total number of lambs weaned (MNLW and TNLW). This analysis utilized a pedigree comprising 13229 animals. Average Information Restricted Maximum Likelihood (AIREML) based Animal Linear Mixed Model estimations for the decomposition of (co)variance components were implemented based on pedigree-derived numerator relationship matrix by also accounting for the number of parities as a fixed factor. Low to moderate heritability estimates, ranging between 0.29 and 0.42, were observed for the lifetime productivity traits of the breed. A wide range of genetic and phenotypic correlations (between −0.56 and 0.99) was observed among the traits of interest. The outcomes of the study are anticipated to significantly enhance the global sheep production systems by uncovering the essential parameters for incorporating ewe’s lifetime reproductive performance and productivity into the selection indices. This will also benefit Central Anatolian Merino farmers, who form a large proportion of sheep producers in Turkey.

Intelligent Program Correction and Evaluation System

The growing popularity of computing applications has sparked the interest of students in computer programming languages. Minor mistakes are prevalent while writing small code blocks due to the coder’s lack of knowledge and carelessness. Instead of merely providing syntax warnings, it would be better to offer developers with an Integrated Development Environment (IDE) that can automatically correct short code blocks containing mistakes. This makes code composition easier and more time-efficient, thus improving the efficacy of large-scale development environments. Because Python is becoming more popular, the goal of our study is to enhance the efficiency of writing Python code by offering an automatic code-correcting approach. Furthermore, automatic program evaluation has been performed to assist in the debugging of small code blocks, which will ultimately be employed in the creation of real-time computer applications. The proposed technique would be useful for new learners who wish to create small Python code blocks for ease of writing and debugging on online platforms (like edX, Coursera, and Udacity). One of the major contributions of the project is to create an erroneous dataset of Python coding that contains all potential forms of probable syntax errors. The dataset induces variety through the use of multiple coding templates and is used to train deep learning models. We used the state-of-the-art text-to-text T5 transformer network model to automatically repair and evaluate the incorrect code. The outcomes of auto-correction are examined using the ROUGE and BLEU scores, as well as accuracy. The model corrects Python code with single, double, and the multiple number of errors with greater than 80% accuracy. Similarly, the performance of the basic T5 transformer network for program auto-evaluation with and without mistakes has been examined, and the model achieves greater than 65% accuracy in both cases. The proposed T5 base transformer outperforms the SOTA auto-correction models in terms of accuracy, according to a comparison study of the proposed method with the earlier techniques for auto-correcting codes.

Cage Nanofillers' Influence on Fire Hazard and Toxic Gases Emitted during Thermal Decomposition of Polyurethane Foam.

Polyurethane (PUR), as an engineering polymer, is widely used in many sectors of industries. However, the high fire risks associated with PUR, including the smoke density, a high heat release rate, and the toxicity of combustion products limit its applications in many fields. This paper presents the influence of silsesquioxane fillers, alone and in a synergistic system with halogen-free flame-retardant compounds, on reducing the fire hazard of polyurethane foams. The flammability of PUR composites was determined with the use of a pyrolysis combustion flow calorimeter (PCFC) and a cone calorimeter. The flammability results were supplemented with smoke emission values obtained with the use of a smoke density chamber (SDC) and toxicometric indexes. Toxicometric indexes were determined with the use of an innovative method consisting of a thermo-balance connected to a gas analyzer with the use of a heated transfer line. The obtained test results clearly indicate that the used silsesquioxane compounds, especially in combination with organic phosphorus compounds, reduced the fire risk, as expressed by parameters such as the maximum heat release rate (HRRmax), the total heat release rate (THR), and the maximum smoke density (SDmax). The flame-retardant non-halogen system also reduced the amounts of toxic gases emitted during the decomposition of PUR, especially NOx, HCN, NH3, CO and CO2. According to the literature review, complex studies on the fire hazard of a system of POSS-phosphorus compounds in the PUR matrix have not been published yet. This article presents the complex results of studies, indicating that the POSS-phosphorous compound system can be treated as an alternative to toxic halogen flame-retardant compounds in order to decrease the fire hazard of PUR foam.

Renewable cycle for CO2 decomposing by liquid metals at ambient conditions

The decomposition of carbon dioxide (CO2) is a potential negative carbon technology, and an effective way to achieve carbon recycling by converting CO2 into high value-added chemicals. However, the CO2 conversion usually requires harsh conditions, complex processes, and high energy consumption, which seriously limit its application and development. Here, we reported a new strategy for direct decomposition and utilization of CO2 under mild conditions based on liquid metals, in which the CO2 was transformed into carbon, corresponding efficiency is approximately 1.125 ml/(g·h). While the oxygen reacted with liquid metals to form Ga2O3. Furthermore, the oxide by-products can be reduced to the liquid metals using the hydrogen at 800 °C for 10.0 h, which generated from water splitting by solar-driven, whereas 34.33% of liquid metals restore their original properties and can be utilized for further recycling. This provided a novel approach to the decomposition and renewable recycling of CO2.

Improving the efficiency of CO2 methanation using a combination of plasma and molecular sieves

In recent years, the chemical reactions with plasma catalysis have been attracted attention. The interaction between plasma ant catalyst can wide the process window, realizing the low pressure and low temperature processes with various catalysts. However, the wide process range make it difficult to optimization for social implement. The key lies in elucidating the reaction mechanism, predicting reactions through numerical simulations, and deriving optimal conditions. On the other hand, recent research has suggested that the use of molecular sieves (MS) can improve methanation efficiency. This can be combined with catalysts, offering new potential applications of MS in chemical reactions. Here, we investigated the more efficient combination of plasma and MS and their reaction mechanisms. As a result, it was found that: 1. The use of MS reduces the oxidation source in the gas phase, leading to an increase in methanation efficiency by suppressing reverse reactions. 2. The adsorption effect of MS, which suppress the reverse reaction, increases with higher pressure. 3. MS in plasma decrease the energy in plasma decrease the energy within the plasma, reducing the CO2 decomposition rate due to electron impact.

Synthesis of an Innovative Framework of Mesoporous Catalyst (Kangolite) by Simple Approach to Promote the Catalytic Activity for CO2 Decomposition

Synthesis of an Innovative Framework of Mesoporous Catalyst (Kangolite) by Simple Approach to Promote the Catalytic Activity for CO2 Decomposition

Leveraging Expertise in Thermal Catalysis to Understand Plasma Catalysis.

Best practices in testing heterogeneous catalysts are translated to plasma-catalytic experiments. Independent determination of plasma-catalytic and plasma-chemical contributions is essential. Non-porous catalyst particles are preferred because active sites inside sub-micron pores cannot contribute. Temperature variation is needed to determine kinetics, despite the complexity of thermal effects in plasma. Rigorous checks on catalyst deactivation and mass balance are needed. Plasma enhanced reversed reactions should be minimized by keeping conversion low and far from thermodynamic equilibrium, preventing underestimation of the rate of forward reaction. In contrast, plasma-catalytic studies often aim at conversions surpassing thermodynamic equilibrium, not obtaining any information on kinetics. Calculation of catalyst activity per active sites (turn-over-frequency) requires also appropriate characterization to determine the number of active sites. The relationship between kinetics and thermodynamics for plasma-catalysis is discussed using endothermic decomposition of CO2 and exothermic synthesis of ammonia from N2 and H2 as examples. Assuming Langmuir-Hinshelwood and Eley-Rideal mechanisms, the effect of excitation of reactant molecules on activation barriers and surface coverages are discussed, influencing reaction rates. The consequences of reversed reactions are considered. Plasma-catalysis with catalysts applied for thermal catalysis at much higher temperature should be avoided, as adsorbed species are bonded too strongly resulting in low rates.

Leveraging Expertise in Thermal Catalysis to Understand Plasma Catalysis

AbstractBest practices in testing heterogeneous catalysts are translated to plasma‐catalytic experiments. Independent determination of plasma‐catalytic and plasma‐chemical contributions is essential. Non‐porous catalyst particles are preferred because active sites inside sub‐micron pores cannot contribute. Temperature variation is needed to determine kinetics, despite the complexity of thermal effects in plasma. Rigorous checks on catalyst deactivation and mass balance are needed. Plasma enhanced reversed reactions should be minimized by keeping conversion low and far from thermodynamic equilibrium, preventing underestimation of the rate of forward reaction. In contrast, plasma‐catalytic studies often aim at conversions surpassing thermodynamic equilibrium, not obtaining any information on kinetics. Calculation of catalyst activity per active sites (turn‐over‐frequency) requires also appropriate characterization to determine the number of active sites. The relationship between kinetics and thermodynamics for plasma‐catalysis is discussed using endothermic decomposition of CO2 and exothermic synthesis of ammonia from N2 and H2 as examples. Assuming Langmuir–Hinshelwood and Eley‐Rideal mechanisms, the effect of excitation of reactant molecules on activation barriers and surface coverages are discussed, influencing reaction rates. The consequences of reversed reactions are considered. Plasma‐catalysis with catalysts applied for thermal catalysis at much higher temperature should be avoided, as adsorbed species are bonded too strongly resulting in low rates.