New Catalyst Found For Electrocatalytic CO2 Recycling

Tokyo University of Science researchers have developed novel in-liquid plasma-treated titanium dioxide electrode decorated with silver nanoparticles to facilitate enhanced conversion of carbon dioxide to useful products, such as syngas, a clean alternative to fossil fuels.

The work was made available and published in the journal Science of the Total Environment.

Carbon dioxide can be electrocatalytically reduced to useful resources using conventional catalysts such as gold or lead supported on conductive carbon. However, the high pH environment near electrodes often degrades the catalyst support, rendering them ineffective.

The conversion of atmospheric carbon dioxide (CO₂) to useful resources such as carbon monoxide, formic acid, and methanol and their byproducts is considered a promising route generating economic value.

Process Diagram For Recycling CO2 To Useful Chemicals. Image Credit: Tokyo University of Science. For a larger version of the image and more information click the press release link.

One approach to CO₂ conversion is through electrocatalytic reduction. This process utilizes conventional catalysts, such as lead, silver, tin, copper, gold etc. supported on conductive carbon as electrode material for selectively CO₂ reduction. However, the electrode is often exposed to a high pH environment of the electrolyte during electrocatalysis, which can degrade the catalyst support and is a cause of major concern.

To address this challenge, a team of researchers, led by Mr. Kai Takagi and Prof. Chiaki Terashima from Graduate School of Science and Technology and Research Institute for Science and Technology at Tokyo University of Science (TUS) in Japan, has recently developed a catalyst support based on titanium dioxide (TiO₂) powder, a compound commonly used in sunscreen, paints, coatings, toothpaste, plastics, paper, pharmaceuticals, and food coloring, as an alternative to carbon for facilitating effective CO₂ reduction.

The researchers first carried out surface treatment using safe and inexpensive in-liquid plasma to improve the electrochemical properties of TiO₂.

Prof. Terashima noted, “The in-liquid plasma-treated TiO₂ maintained its particle shape and crystal structure. Additionally, elemental analysis and evaluation of the interfacial bonding state and electrochemical properties of TiO₂ revealed that the redox peaks corresponding to Ti⁴⁺ and Ti³⁺ derived from TiO₂ disappeared and the hydrogen overvoltage decreased.”

These observations led the team to conclude that tungsten coating or doping occurred on some portions of the reduced TiO₂ surface.

The researchers then used the TiO₂ as a carrier and loaded it with silver nanoparticles (AgNPs), which act as catalysts, to develop a gas diffusion electrode for CO₂ reduction. While untreated TiO₂ exhibited high selectivity for CO₂ and carbon black, in-liquid plasma-treated TiO₂ with 40 wt% AgNP loading demonstrated increased hydrogen production and enhanced catalytic performance.

Given that a suitable ratio of hydrogen to carbon monoxide is important for effective CO₂ reduction, the presented technology, thus, has tremendous potential for converting CO₂ to useful byproducts, such as syngas, which is considered a clean fuel with very high industrial value.

Additionally, the electrocatalytic reduction of CO₂ can be integrated with renewable energy sources, such as solar panels or wind power, for sustainable and environmentally friendly CO₂ conversion. Therefore, this work is a significant step towards efficiently tackling greenhouse gas emissions and fighting climate change.

Prof. Terashima concluded with, “Hopefully, the present study will promote research on technologies for carbon neutrality and carbon recycling, in alignment with the United Nations Sustainable Development Goals 7, 12, and 13 on affordable and clean energy, responsible consumption and production, and climate action, respectively. These, in turn, will open doors to the realization of a carbon-neutral and sustainable future.”

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Recycling CO₂ has to be part of humanity getting into a current carbon cycle with the planet. Without CO₂ recycling the balance needed will not likely be achieved. The idea of 10 billion people using carbon sources for fueling an energy rich existence seems to be a major mess even if the sootiness is minimized and the secondary pollution chemicals are minimized.

But if carbon resources are recycled there is little limit to how high standards of living can get for many billions of people. Carbon itself is a great store of energy and can store immense amounts of hydrogen. It would be the natural thing to do as its just what nature has been doing for hundreds of millions of years.

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