Flow Electrolyzer Mass Spectrometry with a Gas-Diffusion Electrode Design.

Operando mass spectrometry is a powerful technique to probe reaction intermediates near the surface of catalyst in electrochemical systems. For electrochemical reactions involving gas reactants, conventional operando mass spectrometry struggles in detecting reaction intermediates because the batch-type electrochemical reactor can only handle a very limited current density due to the low solubility of gas reactant(s). Herein, we developed a new technique, namely flow electrolyzer mass spectrometry (FEMS), by incorporating a gas-diffusion electrode design, which enables the detection of reactive volatile or gaseous species at high operating current densities (>100 mA cm-2 ). We investigated the electrochemical carbon monoxide reduction reaction (eCORR) on polycrystalline copper and elucidated the oxygen incorporation mechanism in the acetaldehyde formation. Combining FEMS and isotopic labelling, we showed that the oxygen in the as-formed acetaldehyde intermediate originates from the reactant CO, while ethanol and n-propanol contained mainly solvent oxygen. The observation provides direct experimental evidence of an isotopic scrambling mechanism.

Formation of carbon-nitrogen bonds in carbon monoxide electrolysis.

The electroreduction of CO2 is a promising technology for carbon utilization. Although electrolysis of CO2 or CO2-derived CO can generate important industrial multicarbon feedstocks such as ethylene, ethanol, n-propanol and acetate, most efforts have been devoted to promoting C-C bond formation. Here, we demonstrate that C-N bonds can be formed through co-electrolysis of CO and NH3 with acetamide selectivity of nearly 40% at industrially relevant reaction rates. Full-solvent quantum mechanical calculations show that acetamide forms through nucleophilic addition of NH3 to a surface-bound ketene intermediate, a step that is in competition with OH- addition, which leads to acetate. The C-N formation mechanism was successfully extended to a series of amide products through amine nucleophilic attack on the ketene intermediate. This strategy enables us to form carbon-heteroatom bonds through the electroreduction of CO, expanding the scope of products available from CO2 reduction.

A Highly Porous Copper Electrocatalyst for Carbon Dioxide Reduction.

Electrochemical reduction of carbon dioxide (CO2 ) is an appealing approach toward tackling climate change associated with atmospheric CO2 emissions. This approach uses CO2 as the carbon feedstock to produce value-added chemicals, resulting in a carbon-neutral (or even carbon-negative) process for chemical production. Many efforts have been devoted to the development of CO2 electrolysis devices that can be operated at industrially relevant rates; however, limited progress has been made, especially for valuable C2+ products. Herein, a nanoporous copper CO2 reduction catalyst is synthesized and integrated into a microfluidic CO2 flow cell electrolyzer. The CO2 electrolyzer exhibits a current density of 653 mA cm-2 with a C2+ product selectivity of ≈62% at an applied potential of -0.67 V (vs reversible hydrogen electrode). The highly porous electrode structure facilitates rapid gas transport across the electrode-electrolyte interface at high current densities. Further investigations on electrolyte effects reveal that the surface pH value is substantially different from the pH of bulk electrolyte, especially for nonbuffering near-neutral electrolytes when operating at high currents.