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Reverse water gas shift (RWGS) competes with methanation as a direct pathway in the CO2 recycling route, with methanation being a dominant process in the low-temperature window and RWGS at higher temperatures. This work showcases the design of multi-component catalysts for a full-temperature-range RWGS behavior by suppressing the methanation reaction at low temperatures. The addition of alkali promoters (Na, K, and Cs) to the reference Ni/CeO2 catalyst allows identifying a clear trend in RWGS activation promotion in both low- and high-temperature ranges. Our characterization data evidence changes in the electronic, structural, and textural properties of the reference catalyst when promoted with selected dopants. Such modifications are crucial to displaying an advanced RWGS performance. Among the studied promoters, Cs leads to a more substantial impact on the catalytic activity. Beyond the improved CO selectivity, our best performing catalyst maintains high conversion levels for long-term runs in cyclable temperature ranges, showcasing the versatility of this catalyst for different operating conditions. All in all, this work provides an illustrative example of the impact of promoters on fine-tuning the selectivity of a CO2 conversion process, opening new opportunities for CO2 utilization strategies enabled by multi-component catalysts.

Reverse water gas shift (RWGS) competes with methanation as a direct pathway in the CO2 recycling route, with methanation being a dominant process in the low-temperature window and RWGS at higher temperatures. This work showcases the design of multi-component catalysts for a full-temperature-range RWGS behavior by suppressing the methanation reaction at low temperatures. The addition of alkali promoters (Na, K, and Cs) to the reference Ni/CeO2 catalyst allows identifying a clear trend in RWGS activation promotion in both low- and high-temperature ranges. Our characterization data evidence changes in the electronic, structural, and textural properties of the reference catalyst when promoted with selected dopants. Such modifications are crucial to displaying an advanced RWGS performance. Among the studied promoters, Cs leads to a more substantial impact on the catalytic activity. Beyond the improved CO selectivity, our best performing catalyst maintains high conversion levels for long-term runs in cyclable temperature ranges, showcasing the versatility of this catalyst for different operating conditions. All in all, this work provides an illustrative example of the impact of promoters on fine-tuning the selectivity of a CO2 conversion process, opening new opportunities for CO2 utilization strategies enabled by multi-component catalysts.

The reverse water–gas shift reaction (RWGS) reaction represents a direct route for CO2 conversion whose selectivity significantly depends on the selected catalyst. In this work, a new family of bimetallic iron–copper oxide catalysts supported on ceria-alumina with various Fe/Cu oxides ratios were investigated for the RWGS reaction. Additionally, bare Fe-based and Bare Cu-based catalysts were synthesized for comparison. Our results demonstrate that the developed bimetallic Fe–Cu catalysts present a remarkable enhancement of catalytic performance when compared to monometallic systems, especially at the so-called “low-temperature range” for RWGS. Characterization results evidence that Cu species undergo different states on the catalytic surface during the reaction, wherein the formed metallic Cu is linked to the catalytic activity via the strength of the interaction with the multioxide phases, such as Fe3O4/CeO2, while the copper-dopped ceria could contribute to the promotion of CO selectivity. Besides, we identify that the Fe/Cu oxides mass ratio of 0.25/0.75 is an optimal formulation rendering highly commendable CO2 conversion levels at 450 °C with excellent selectivity and stability for long-term runs. Very importantly, without preactivation, our multicomponent materials still display an optimum performance which have a potential realistic application from cost perspective than other Cu-based catalysts. Overall, this work showcases a strategy to design highly effective multicomponent Fe–Cu catalysts for CO2 conversion via RWGS.

MAX phases are layered ternary carbides or nitrides that are attractive for catalysis applications due to their unusual set of properties. They show high thermal stability like ceramics, but they are also tough, ductile, and good conductors of heat and electricity like metals. Here, we study the potential of the Ti3AlC2 MAX phase as a support for molybdenum oxide for the reverse water–gas shift (RWGS) reaction, comparing this new catalyst to more traditional materials. The catalyst showed higher turnover frequency values than MoO3/TiO2 and MoO3/Al2O3 catalysts, due to the outstanding electronic properties of the Ti3AlC2 support. We observed a charge transfer effect from the electronically rich Ti3AlC2 MAX phase to the catalyst surface, which in turn enhances the reducibility of MoO3 species during reaction. The redox properties of the MoO3/Ti3AlC2 catalyst improve its RWGS intrinsic activity compared to TiO2- and Al2O3-based catalysts.

Advanced catalytic technologies are crucial to enable the transition toward a low-carbon industry with minimized CO2 emissions. This paper showcases the application of highly effective Ru-promoted Ni-based catalysts for gas-phase CO2 upgrading: CO2 methanation and reverse water–gas shift. The addition of small amounts of Ru results in a remarkable enhancement of CO2 conversion and selectivity. The bimetallic Ru-Ni catalyst displays greater metallic dispersion, tuned electronic properties and outstanding stability for long-term runs, a mandatory requisite for its implementation in actual CO2 conversion units. The singularity of our advanced catalyst lays on its capacity to work effectively for both the CO2 methanation and the reverse water–gas shift, allowing end-product flexibility by adjusting the reactor temperature. Such versatility opens a big range of possibilities to adapt this technology in heavy carbon industries whose net CO2 emissions represent a big share in the global greenhouse gases emissions.

This work showcases an innovative route for biocompound upgrading via hydrodeoxygenation (HDO) reactions, eliminating the need for external high-pressure hydrogen supply. We propose the use of water as reaction media and the utilization of multifunctional catalysts that are able to conduct multiple steps such as water activation and HDO. In this study, we validate our hypothesis in a high-pressure batch reactor process using guaiacol as a model compound and multicomponent Ni-based catalysts. In particular, a comparison between ceria-supported and carbon/ceria-supported samples is established, the carbon-based materials being the suitable choice for this reaction. The physicochemical study by X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray diffraction, and temperature-programmed reduction reveals the greater dispersion of Ni clusters and the strong metal-support interaction in the carbon/ceria-based samples accounting for the enhanced performance. In addition, the characterization of the spent samples points out the resistance of our catalysts toward sintering and coking. Overall, the novel catalytic approach proposed in this paper opens new research possibilities to achieve low-cost bio-oil upgrading processes.

Understanding/visualizing the established interactions between gases and adsorbents is mandatory to implement better performance materials in adsorption/separation processes. Here we report the unique behavior of a rare example of a hemilabile chiral three-dimensional metal–organic framework (MOF) with an unprecedented qtz-e-type topology, with formula CuII2(S,S)-hismox·5H2O (1) (hismox = bis[(S)-histidine]oxalyl diamide). 1 exhibits a continuous and reversible breathing behavior, based on the hemilability of carboxylate groups from l-histidine. In situ powder (PXRD) and single crystal X-ray diffraction (SCXRD) using synchrotron radiation allowed us to unveil the crystal structures of four different host–guest adsorbates (Ar@1, N2@1, CO2@1, and C3H6@1), rationalize the breathing motion, and unravel the mechanisms governing the adsorption of these gases. Then this information was transferred to implement efficient separations of mixtures of industrial and environmental relevance, CO2/N2, CO2/CH4, and C3H8/C3H6, using 1 in packed columns as the stationary phase and dispersed in a mixed matrix membrane.

Materials able to produce the reduction of nitrate from water without the need of a metal catalyst and with avoiding the use of gaseous hydrogen have been developed by combining the synergistic properties of titania and two conducting polymers. Polymerization of aniline and pyrrol on titanium dioxide in the presence of two different oxidants/dopants (iron trichloride or potassium persulfate) has been evaluated. The resulting hybrid materials have good thermal stability imparted by the titania counterpart, and a considerable conductivity provided by the conducting polymers. The capability of the hybrid materials of reducing aqueous nitrate has been assessed and compared to the catalytic hydrogenation of nitrate using a platinum catalyst supported on these hybrid synthesized materials. The mechanism of nitrate abatement implies adsorption of nitrate on the polymer by ion exchange with the dopant anion, followed by the reduction of nitrate. The electron transfer from titania to the conducting polymer in the hybrid material favors the reductive ability of the polymer, in such a way that nitrate is selectively reduced with a very low production of undesirable side products. The obtained results show that the activity and selectivity of the catalytic reduction of nitrate with dihydrogen in the presence of a platinum catalyst supported on the hybrid materials are considerably lower than those of the metal-free nanocomposites.