Thin-water-film-enhanced TiO₂-based catalyst for CO₂ hydrogenation to formic acid

Abstract

Carbon dioxide (CO2) hydrogenation can not only mitigate global warming, but also produce value-added chemicals. Herein, we report a novel three-phase catalytic system with an in-situ generated and dynamically updated...

Temperature, pressure, and adsorption‐dependent redox potentials: I. Processes of CO2 reduction to value‐added compounds

“…3 The utilization of cheap, safe, and abundant CO 2 as a feedstock in industrial processes to produce value−added chemicals and fuels is the most attractive practice that can not only lessen atmospheric CO 2 but also alleviate the energy crisis caused by fossil fuel depletion. 2,6 The semireactions of CO 2 reduction into common high-value C1 and C2 substances including carbon monoxide (CO), formic acid (HCOOH), formaldehyde (HCHO), methanol (CH 3 OH), methane (CH 4 ), oxalic acid (H 2 C 2 O 4 ), acetic acid (CH 3 COOH), acetaldehyde (CH 3 CHO), ethanol (CH 3 CH 2 OH), ethylene (C 2 H 4 ), and ethane (C 2 H 6 ) are shown in Equations ( 1)- (11). Moreover, hydrogen (H 2 ) and water are typically used as the reducing agent for CO 2 , whose semireactions are listed in Equation (12) and Equation (13), respectively.…”

Thermo-photo catalysis: a whole greater than the sum of its parts

“…Namely, the surface active sites of the catalyst should be adequately exposed to reactants, and meanwhile the products can be fast desorbed from catalyst surface to regenerate the active sites. 95,170 Only with the guaranteed mass transfer can the catalytic reaction proceed efficiently.…”

“…While, if some reactants are in gas phase such as CO 2 reduction by water, the suspension system would limit the accessibility of the catalyst toward gas reactants unless these gas reactants possess high solubilities in the liquid. 170,173,174 While, the influence of the product phase on catalytic efficiency is not significant since the stirred catalyst suspension is advantageous for cleaning active sites, especially for the removal of soluble products from catalyst surface to the liquid solvent. 28,95,173 For example, in partial oxidation of CH 4 , water suppressed the accessibility of CH 4 but promoted the desorption of liquid oxygenates, leading to an overall enhancement in catalytic efficiency.…”

“…For thermo-photo catalysis, three aspects of mass transfer are involved, including the diffusion of reactants and products through liquid or gas media, adsorption onto and desorption from catalyst surface, and transfer of intermediate species across catalyst surface. 28,90,170 The diffusion coefficient in liquid phase (D L ) can be calculated via Stokes-Einstein equation (eqn (4)).…”

“…While, if some reactants are in gas phase such as CO 2 reduction by water, the suspension system would limit the accessibility of the catalyst toward gas reactants unless these gas reactants possess high solubilities in the liquid. 170,173,174…”