CO2 Conversion: Breakthrough Catalyst Turns Climate Change’s Enemy into a Valuable Resource

“Defects tune strong metal-support interactions” is a unique approach to design a CO2 reduction nanocatalyst with excellent efficiency and stability. Acknowledgment: Mr. Rajesh Belgamwar and Prof. Vivek Polshettiwar

A research team has developed a highly efficient and stable copper-based catalyst (DFNS/TiO2-Cu) to convert CO2 to CO, with a CO productivity of 5350 mmol g-1 h-1 and a selectivity of 99.8%. The catalyst remained stable for more than 200 h, and in situ studies highlighted the importance of defect sites in tuning strong metal-support interactions.

The intensive use of fossil fuels to drive industrial processes and human activity has resulted in increasingly excessive anthropogenic CO emissions.₂ in our atmosphere, exceeding the 400 ppm level. This extremely high atmospheric CO concentration₂ has created a series of negative consequences for our planet’s climate system. However, CO₂ can be a strategic carbon resource for synthesizing valuable chemicals and fuels. There have been many reports on noble metal catalysts, but their applications were limited due to their moderate catalytic performance and high cost. In the family of base metal catalysts, Cu-based catalysts are among the most versatile, with good potential in many industrial processes. Unfortunately, the low Taman temperature of copper and the resulting surface migration cause sintering of the nanoparticles during the reaction, limiting their activity and long-term stability.

In this work, the research team of prof. led by Vivek Polshetivar at Tata Institute of Fundamental Research (TIFR) in Mumbai asked how to improve the catalytic activity and stability of Cu-catalyst using the concept of strong metal support interaction (SMSI) and defect site cooperation?

They reported a catalyst with active copper sites loaded on titanium oxide-coated dendritic fibrous nanosilica (DFNS/TiO)₂-Cu)CO₂ to CO conversion. The fibrous morphology and large surface area of ​​DFNS/TiO₂ allowed better dispersion and loading of active sites of Cu NPs. This catalyst showed excellent CO catalytic performance₂ decrease with CO productivity of 5350 mmol g^-1 h^-1 (ie, 53506 mmol g_Cu^-1 h^-1), is superior to all copper-based thermal catalysts. In particular, DFNS/TiO₂-Cu10 showed 99.8% selectivity to CO and was stable for at least 200 h. Defect controlled strong metal support interaction between Cu and TiO₂ kept the copper nanoparticles firmly anchored on the support surface and provided excellent catalyst stability.

EELS studies, in situ diffuse reflectance infrared Fourier transform spectroscopy, H₂– Temperature programmed reduction, density functional theory calculations and long-term stability indicated strong interactions between copper sites and Ti³⁺ websites, which ensured good stability and dispersion of active copper sites. On the spot studies provided insight into the role of defect sites (ie³⁺ and O-vacancies) in SMSI tuning. On the spot time-resolved Fourier transform infrared indicated that CO₂ did not directly dissociate to form CO, whereas in situ Raman and in situ The UV-DRS study showed that the intensity of oxygen vacancies and Ti³⁺ centers gradually decreased after the introduction of CO₂ the gas enters the reactor chamber and gradually expands, exposing it to hydrogen. It indicated that the CO₂ The conversion of CO followed a redox pathway assisted by hydrogen.

Excellent catalytic performance of DFNS/TiO₂– Cu and in situ Mechanical studies indicated the possibility of defects in the tuning of strong metal-support interactions. This approach can lead to the design of catalytic systems using different active sites and defective supports.

Reference: “Defects tune the strong metal-support interactions in copper supported by defective TiO catalysts CO₂ Reduction’ by Rajesh Belgamwar, Rishi Verma, Tisita Das, Sudip Chakraborty, Pradip Sarawade and Vivek Polshettiwar, April 5, 2023, Journal of the American Chemical Society.
DOI: 10.1021/jacs.3c01336

Funding: Department of Atomic Energy (DAE), Government of India, India Innovation Mission, Department of Science and Technology, Government of India