Thermodynamic Considerations for Optimizing Selective CO₂ Reduction by Molecular Catalysts

Abstract

Energetically efficient electrocatalysts with high product selectivity are desirable targets for sustainable chemical fuel generation using renewable electricity. Recycling CO 2 by reduction to more energy dense products would support a carbon-neutral cycle that mitigates the intermittency of renewable energy sources. Conversion of CO 2 to more saturated products typically requires proton equivalents. Complications with product selectivity stem from competitive reactions between H + or CO 2 at shared intermediates. We describe generalized catalytic cycles for H 2 , CO, and HCO 2 – formation that are commonly proposed in inorganic molecular catalysts. Thermodynamic considerations and trends for the reactions of H + or CO 2 at key intermediates are outlined. A quantitative understanding of intermediate catalytic steps is key to designing systems that display high selectivity while promoting energetically efficient catalysis by minimizing the overall energy landscape. For CO 2 reduction to CO, we describe how an enzymatic active site motif facilitates efficient and selective catalysis and highlight relevant examples from synthetic systems.

Transition metal-based catalysts for the electrochemical CO2reduction: from atoms and molecules to nanostructured materials

“…Following this approach, FEs as high as 68% or 72% for HCOOH were obtained by adding 40 mM of quinuclidine or trimethylamine to a 40 mM PrOH solution of 1, respectively. 106 In contrast with the conventional pathway for HCOOH formation based on net CO 2 insertion into a reactive M-H bond (a common intermediate to HER), 107,108 this alternative strategy uses weak acids to produce HCOOH, circumventing the formation of undesired hydride species.…”

Enhanced Electrocatalytic Activity of a Zinc Porphyrin for CO2 Reduction: Cooperative Effects of Triazole Units in the Second Coordination Sphere

“…This knowledge has led to the successful design of molecular catalysts for carbon dioxide reduction, [2] hydrogen evolution reaction, [3] hydrogen oxidation, [4] and water oxidation [5] . Higher coordination sphere in ligands can promote more selective binding of the substrate to the metal center, facilitating proton and electron donation [3a, 6] . Common substituents utilized in second coordination sphere coordination complexes include amines, [2b, 7] phenols, [2c, 8] urea, [9] amides, [10] carboxylic acids, [11] triazoles, [12] and imidazoles [13] .…”

What Fluorine Can Do in CO2 Chemistry: Applications from Homogeneous to Heterogeneous Systems

“…[4][5][6] In this respect, considering the practical conditions encountered in the process of fossil fuels combustion, [7] numerous physical or chemical sorption technologies and approaches have been demonstrated in the presence of liquid/solid systems including ionic liquids (ILs), [8] porous liquids (PLs), [9] carbonaceous materials, [10] metal À organic frameworks (MOFs), [11][12][13] zeolites, [14] covalent organic frameworks (COFs), [15] membranes, [16] porous organic polymers (POPs), [17] and so on. In addition, CO 2 is an environmentally friendly and renewable C1 building block with easy availability and found in abundance, which could be converted into high-value added chemicals or alternative fuels through the formation of CÀ O, CÀ C, CÀ N, or CÀ H bonds [18][19][20] achieved via thermo-catalytic, [21,22] electro-catalytic, [23][24][25][26] and photo-catalytic [27] pathways in the presence of homogeneous or heterogeneous catalytic systems.…”