Carbon dioxide capture and reduction (CCR) process emerges as an efficient catalytic strategy for CO₂ capture and conversion to valuable chemicals. K-promoted Cu/Al₂O₃ catalysts exhibited promising CO₂ capture efficiency and highly selective conversion to syngas (CO + H₂). The dynamic nature of the Cu-K system at reaction conditions complicates the identification of the catalytically active phase and surface sites. The present work aims at more precise understanding of the roles of the potassium and copper and the contribution of the metal oxide support. While γ-Al₂O₃ guarantees high dispersion and destabilisation of the potassium phase, potassium and copper act synergistically to remove CO₂ from diluted streams and promote fast regeneration of the active phase for CO₂ capture releasing CO while passing H₂. A temperature of 350℃ is found necessary to activate H₂ dissociation and generate the active sites for CO₂ capture. The effects of synthesis parameters on the CCR activity are also described by combination of ex-situ characterisation of the materials and catalytic testing.

Dynamic coke-mediated dry reforming of methane (DC-DRM) is an unsteady-state strategy to overcome the limitations of co-feed operation, including the fast deactivation of the catalysts and the loss of valuable H₂ in the reverse water gas-shift reaction. This paper proves the feasibility of DC-DRM on Ni-based catalytic systems, identifying suitable metal oxides supports and evaluating the role of metallic promoters. A La-promoted Ni/ZrO₂ catalyst exhibited excellent and stable catalytic performances at 800 °C approaching complete conversion of the CH₄ and CO₂ reactant pulses in the reaction loop, and separation of the H₂ and CO product streams. Adding the redox functionality of reducible oxides (TiO₂) in the catalyst support is demonstrated as a powerful tool to enable direct formation of syngas in the methane pulse with control on the H₂/CO ratio.

The electrochemical CO₂ reduction reaction (CO₂RR) is an attractive method to produce renewable fuel and chemical feedstock using clean energy sources. Formate production represents one of the most economical target products from CO₂RR but is primarily produced using post-transition metal catalysts that require comparatively high overpotentials. Here a composition of bimetallic Cu–Pd is formulated on 2D Ti₃C₂T_x (MXene) nanosheets that are lyophilized into a highly porous 3D aerogel, resulting in formate production much more efficient than post-transition metals. Using a membrane electrode assembly (MEA), formate selectivities >90% are achieved with a current density of 150 mA cm⁻² resulting in the highest ever reported overall energy efficiency of 47% (cell potentials of −2.8 V), over 5 h of operation. A comparable Cu-Pd aerogel achieves near-unity CO production without the MXene templating. This simple strategy represents an important step toward the experimental demonstration of 3D-MXenes-based electrocatalysts for CO₂RR application and opens a new platform for the fabrication of macroscale aerogel MXene-based electrocatalysts.

Direct valorization of methane via oxidative coupling of methane (OCM) is an encouraging alternative to conventional oil-based processes for the production of light hydrocarbons (ethane and ethylene). Abundant, inexpensive simple oxides such as MgO and La₂O₃ possess the ability to selectively activate methane. However, during OCM, the selective conversion to ethane and the following dehydrogenation to ethylene are threatened by the thermodynamically favored partial and total oxidation reactions to form CO and CO₂, respectively. With the aid of spatially resolved operando analysis of temperature and gas concentration along the catalytic bed, we demonstrate the relevance of highly exothermic reaction paths developed in the gas phase, i.e., the homogeneous reaction, during OCM conditions at the front of the catalytic bed, largely determining the total C₂ yield obtained on those systems. With the new insights provided by the analysis of temperature and concentration gradients along the bed, we redefine the positive effect of promoters (Li, Sr), which enhance the influence of catalyst surfaces. The effect of promoters is recognized in the suppression of the exothermic oxidation paths leading to undesired CO_x, thus limiting the formation of hotspots and driving the reaction toward the desired C₂ products.

Integrated CO₂ capture and conversion processes bring the promise of drastic abatement of CO₂ emission together with its valorisation to chemical building blocks such as CH₄ and CO. Isothermal CO₂ capture and reduction (CCR) on a K-promoted Cu/Al₂O₃ was recognised as an effective catalytic strategy for removing CO₂ from diluted stream and converting it to syngas (H₂ + CO) employing green H₂ as reducing agent. The dual functionality of the catalyst is the key of this dynamic process, in which the alkaline metal introduces the capture functionality and copper ensures the selective conversion of the captured CO₂ to CO. However, the highly dynamic state of the catalyst at reaction conditions represents a barrier for the identification of the catalytic mechanism of CCR, which is vital for rational process improvement and design. In this work, we conducted a mechanistic investigation of CCR by means of spatiotemporal operando methodologies, gaining insights into dynamic variation of temperature, gas concentration and reactive surface species in the CCR reactor. The results show the unique potassium state exothermically captures CO₂ as surface carbonates which can be reduced to CO rapidly under H₂ atmosphere. When the surface carbonates are transformed to formates the reaction path is altered and the reduction to CO becomes slower. By designing controlled catalytic experiments, we further demonstrate the active involvement of CO in the capture mechanism and the effectiveness of CO₂ capture in presence of an oxidised surface, extending the perspectives and suitability of CCR to treat actual complex effluent streams.

Industrial-scale reforming of methane is typically carried out with an excess of oxidant to suppress coking of the catalyst. On the other hand, many academic studies on dry reforming employ a CO₂/CH₄ ratio of unity to quickly observe coking which can be reduced by adding a catalyst promoter. In this work, Ni/Al₂O₃ catalysts were tested for dry reforming of methane (CO₂/CH₄=1) with additional regeneration steps to test the resistance against an oxidation treatment. Thereby, we wanted to evaluate catalyst stability for industrial relevance. The effects of three promoters, Cr, Mn and Fe, that differ in their degree of CO₂ interaction, are compared. A higher iron loading on Ni/Al₂O₃ leads to higher stability in dry reforming with lower coke formation. However, the higher the concentration of a promoter with high CO₂ affinity, the quicker the catalyst is oxidized during regeneration with CO₂. Subsequent reduction of a catalyst oxidized with CO₂ leads to considerable sintering in all cases. This sintering induces formation of more coke during dry reforming. On such sintered samples only highly effective promoters in large concentrations still have a noticeable effect compared to unpromoted Ni/Al₂O₃.

Oxidative coupling of methane (OCM) to produce ethane and ethylene is one of the dream reactions of researchers in catalysis. Despite the extensive efforts over the last three decades, our general understanding on OCM is rather poor due to the complexity arising from the reaction network, and also from the various gradients such as temperature and gaseous concentration present in OCM reactors. This chapter highlights reactions active under OCM conditions and how they are interlinked. Special emphasis is given on space-resolved analytical methodologies as promising key enabling tools towards rational development of catalytic materials and processes for OCM.