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Decouple Electrochemical Reduction of Carbon Dioxide to High Value Products

Periodic Reporting for period 2 - DeCO-HVP (Decouple Electrochemical Reduction of Carbon Dioxide to High Value Products)

Reporting period: 2020-04-01 to 2021-09-30

What is the problem/issue being addressed?

The project addresses the need to create carbon neutral carbon feedstocks in the chemical industry from captured and surplus carbon dioxide (CO2). We can achieve it with high pressures and temperatures, over catalysts in a mixture of hydrogen and CO2, but this approach is carbon intensive and uses methane as a source of hydrogen. Another approach to reducing CO2 is by attempting to use electricity to derive hydrocarbons of value. The electrochemical reduction of CO2 is a grand challenge of fundamental research and has only had some moderate successes over the past few decades. The reason the reaction is so challenging is that CO2 is a very stable molecule and to achieve what is essentially reverse combustion to hydrocarbons requires not only energy, but the exact right conditions and a high concentration of CO2. Water is an ideal source of hydrogen to hydrogenate the carbon molecule, but CO2 is not readily dissolved in water to high concentrations. This is especially problematic when you are restricting the reaction site to an electrode surface, as maintaining a high concentration of CO2 is difficult. This project aims to approach electrochemical reduction differently, by separating the electrochemical step from the CO2 reduction.

Why is it important for society?

This research is of importance to society as we depend heavily on fossil derived hydrocarbons for the synthesis of most chemicals in pharmaceuticals, materials, food, as well as for fuels. A move to electrifying the transport sector is only a small aspect of decarbonising industry and reducing our dependence on oil, coal and gas. Converting captured and atmospheric CO2 to commodity chemicals is one way of circumventing the use of fossil fuels and preventing further release of CO2 into the atmosphere. It is a strategy to keep society operating with the same quality of materials and chemicals it is used to, without depending on fossil fuels and contributing further to climate change.

What are the overall objectives?

The main innovative idea is to use electricity to generate solutions capable of reducing the CO2 in a separate process, and then mix the solution with CO2 and a catalyst material in another reaction. It is also evaluating new materials as potential catalysts that will directly reduce CO2 as a gas using a gas diffusion electrode flow reactor.

This project is aiming to demonstrate a proof-of-concept that the electrochemical process of using electricity to drive a chemical reaction can be separated from the chemical reduction of carbon dioxide. This approach would allow the design and implementation of the reactor to be reimagined and scaled into an industrial process. Electrochemical CO2 reduction at present looks to directly convert CO2 at an electrode surface. But this is inherently difficult due to the low solubility of CO2 in water and competing reaction to reduce water to hydrogen. Using flow reactor technology that exists for redox flow batteries and electrolysis, is possible to instead generate a "charged" solution with the potential energy to reduce CO2 chemically. The application of a suitable catalyst will facilitate this, and ideally, prompt selective reduction to a range of hydrocarbon products of value to industry, such as methanol.
Installed and calibrated a new analytical system for product analysis - Gas chromatography with barrier ionisation discharge (GC-BID)

Identified and new homogeneous CO2 reduction catalysts. Evaluation and characterisation studies are ongoing, including computational studies of the catalytic mechansim.

Developed a new approach to online electrochemical mass spectrometry to evaluate CO2 reduction products and catalyst performance with respect to electrode potential. Ongoing.

Established on-line gas product analysis using the GC-BID

Successful synthesis of bimetallic copper and bismuth materials using electrodeposition. Their characterisation and catalytic abiity is being studied.

MXene synthesis developed in-house to give high quality delaminated few layer MXenes.

Range of flow reactors for redox mediator synthesis and CO2 reduction have been designed and fabricated. Most recently a gas diffusion electrode flow reactor has been fabricated and is undergoing preliminary characteriation.
A new flow reactor to couple with mass spectrometry is being optimised and will be a significant tool in CO2 reduction studies going forward. We anticipate being able to screen materials with high throughput and flexibility going forward.

Implementing a gas diffusion electrode flow reactor will permit a change in the reaction dynamics of the catalyst materials being studied. The set-up is already showing promising results.

Study of a new category of iron dithiolene catalyst for homogeneous CO2 reduction.

Demonstration of indirect conversion of CO2 to reduced species using a dispersion of solid catalyst. This proof-of-concept would demonstrate a step-change in how we approach electrochemical CO2 reduction.
Evaluating online gas analysis using GC-BID and a gas diffusion electrode flow reactor
Generating chromium redox mediators to test