Abstract
Two-dimensional pristine M2X MXenes are proposed as highly active catalytic materials for carbon dioxide (CO2) greenhouse gas conversion into carbon monoxide (CO) on the basis of a multiscale modeling approach, coupling calculations carried out in the framework of density functional theory and newly developed kinetic phase diagrams. The extremely facile CO2 conversion into CO leaves the MXene surfaces partially covered by atomic oxygen, recovering its pristine nature by a posterior catalyst regeneration by hydrogen (H2) treatment at high temperatures, with MXenes effectively working as two-step catalysts for the reverse water–gas shift reaction.
Highlights
The ever-growing energy demands to sustain the current society wellness standards has put climate at stake, where one of the major causes of global warming is the anomalous high concentration of carbon dioxide (CO2) greenhouse gas present in the atmosphere.[1]
More appealing than carbon capture and storage (CCS) are carbon capture and utilization (CCU) technologies,[6−8] aimed at using CO2 as a C1 chemical feedstock; by this, CO2 can be chemically converted into other greener and potentially industrially useful chemicals, such as methanol, currently used in fuel cells,[9] or carbon monoxide (CO), which can be later used in the Fischer−Tropsch process, synthesizing Cn hydrocarbons.[10,11]
Inspired by the promising performance in the electrocatalytic and photocatalytic[16] CO2 reduction of a series of MXene-based compounds, including O- and OH-terminated MXenes,[17−19] vacancy-containing MXenes,[20] and even MXene-based composites,[21] and spurred by the aforementioned CCS technology achievement, we show here compelling theoretical evidence based on accurate density functional theory (DFT) simulations and newly developed kinetic phase diagrams of the very high CCU activity of the MXenes family, catalyzing the CO formation; a product that can be subsequently used in methanol synthesis or introduced in Fischer−Tropsch plants to produce hydrocarbons
Summary
The ever-growing energy demands to sustain the current society wellness standards has put climate at stake, where one of the major causes of global warming is the anomalous high concentration of carbon dioxide (CO2) greenhouse gas present in the atmosphere.[1] Actions are being taken to reduce the CO2 emissions, for example, exploiting clean energy sources or even maximizing the energy profit from other existing ones. Exceedingly large amounts of CO2 are and will be poured into the atmosphere, and complementary actions and processes are sought in order to mitigate the climate change. Carbon capture and storage (CCS)[2−4] has been highlighted to eliminate 550 billion CO2 tons in the atmosphere, needed to return to the preindustrial natural situation.[5] For CCS, materials are sought able to anchor CO2 under standard conditions, a task challenged by the CO2 high molecular stability and consequent low activity. More appealing than CCS are carbon capture and utilization (CCU) technologies,[6−8] aimed at using CO2 as a C1 chemical feedstock; by this, CO2 can be chemically converted into other greener and potentially industrially useful chemicals, such as methanol, currently used in fuel cells,[9] or carbon monoxide (CO), which can be later used in the Fischer−Tropsch process, synthesizing Cn hydrocarbons.[10,11] The back-formation of re-usable fuels by CCU while using renewable sources of energy, and other sustainable reagents, for example, hydrogen (H2) from water photocatalysis, conforms a plausible path toward closing the C-cycle
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