Selective CO2 Electrochemical Reduction Enabled by a Tricomponent Copolymer Modifier on a Copper Surface.

Electrochemical CO2 reduction over Cu could provide value-added multicarbon hydrocarbons and alcohols. Despite recent breakthroughs, it remains a significant challenge to design a catalytic system with high product selectivity. Here we demonstrate that a high selectivity of ethylene (55%) and C2+ products (77%) could be achieved by a highly modular tricomponent copolymer modified Cu electrode, rivaling the best performance using other modified polycrystalline Cu foil catalysts. Such a copolymer can be conveniently prepared by a ring-opening metathesis polymerization, thereby offering a new degree of freedom for tuning the selectivity. Control experiments indicate all three components are essential for the selectivity enhancement. A surface characterization showed that the incorporation of a phenylpyridinium component increased the film robustness against delamination. It was also shown that its superior performance is not due to a morphology change of the Cu underneath. Molecular dynamics (MD) simulations indicate that a combination of increased local CO2 concentration, increased porosity for gas diffusion, and the local electric field effect together contribute to the increased ethylene and C2+ product selectivity.

The Formation of CO by Thermal Decomposition of Formic Acid under Electrochemical Conditions of CO2 Reduction.

We report that the thermal decomposition of formic acid to CO may occur under electrochemically-relevant conditions by mild heating. These thermal effects may play a role in the outcome of electrolytic experiments as an artifact of resistive, local heating and illumination. This non-Faradaic reactivity pathway may therefore need consideration in the analysis of electrochemical data on CO2 reduction to formic acid and CO and may become a hindrance in scaleup efforts of these chemical transformations. IR visual thermometry provides evidence of macroscopic heating effects during electrolytic experiments.

Organic reactions for the electrochemical and photochemical production of chemical fuels from CO2--The reduction chemistry of carboxylic acids and derivatives as bent CO2 surrogates.

The present review covers organic transformations involved in the reduction of CO2 to chemical fuels. In particular, we focus on reactions of CO2 with organic molecules to yield carboxylic acid derivatives as a first step in CO2 reduction reaction sequences. These biomimetic initial steps create opportunities for tandem electrochemical/chemical reductions. We draw parallels between long-standing knowledge of CO2 reactivity from organic chemistry, organocatalysis, surface science and electrocatalysis. We point out some possible non-faradaic chemical reactions that may contribute to product distributions in the production of solar fuels from CO2. These reactions may be accelerated by thermal effects such as resistive heating and illumination.

Electrocatalytic Reduction of Nitrogen and Carbon Dioxide to Chemical Fuels: Challenges and Opportunities for a Solar Fuel Device.

Aspects of the electrochemical reduction of nitrogen and carbon dioxide at molecular and heterogeneous catalysts are discussed. We focus on recent advances in the field and touch on some of the remaining challenges in the production of solar fuels from N2 and CO2 with a direct, integrated solar fuel device. As such, we now propose metrics of catalyst assessment for non-H2 solar fuels.