Periodic Reporting for period 1 - NANOconfine (Nanopatterning and nanoconfinement for deterministic control of the local homogeneous and heterogeneous chemical environment in electrocatalytic CO2RR towards C3+ products)
Reporting period: 2021-08-01 to 2023-07-31
Decreasing the anthropogenic carbon emissions is one of the most urgent challenges of our society. Additional EU policies and incentives will be needed to further counter and eventually reverse emissions in the years to come. Capture of CO2 is considered necessary to reach the goal of zero-emission by 2050. The electrocatalytic CO2 reduction reaction (CO2RR) holds the prospect to mitigate carbon emissions and at the same time convert CO2 with renewable electricity into valuable chemicals for energy storage or as precursor for industry. Depending on the number of electrons transferred in the reaction, a variety of oxygenates and hydrocarbons can be obtained with already high selectivity demonstrated for C1 and C2 products. However, for the CO2RR to molecules with three or more carbon atoms (C3+) such as n-propanol, the fundamental knowledge and key-strategies to yield these economically attractive high-energy-density products are still lacking.
In this context, NANOconfine aimed to contribute to the fundamental understanding of the electrocatalytic CO2RR and helped to develop key-strategies to yield these economically attractive chemical products. The project combines imec’s profound expertise on fabrication of nanopatterns and nanomaterials with the know-how on electrochemistry and electrocatalysis. The project goal was to investigate the effect of near-neighbors in nano-patterned co-catalyst systems (e.g. Cu and Ag) with additional confinement for optimal interchange of their reaction intermediates so that they can undergo coupling to higher carbon products. In order to design the optimal electrocatalyst architecture, a systematic approach was proposed to study the following effects on the CO2RR mechanism and product formation: (1) the near neighbor effect of nano-patterned co-catalysts, (2) the confinement of reaction intermediates in regular-arranged vertical SiO2 mesopores (2-10nm) and (3) the confinement and surface chemistry of different mesoporous metal 3D-nanowire networks.
In this context, NANOconfine aimed to contribute to the fundamental understanding of the electrocatalytic CO2RR and helped to develop key-strategies to yield these economically attractive chemical products. The project combines imec’s profound expertise on fabrication of nanopatterns and nanomaterials with the know-how on electrochemistry and electrocatalysis. The project goal was to investigate the effect of near-neighbors in nano-patterned co-catalyst systems (e.g. Cu and Ag) with additional confinement for optimal interchange of their reaction intermediates so that they can undergo coupling to higher carbon products. In order to design the optimal electrocatalyst architecture, a systematic approach was proposed to study the following effects on the CO2RR mechanism and product formation: (1) the near neighbor effect of nano-patterned co-catalysts, (2) the confinement of reaction intermediates in regular-arranged vertical SiO2 mesopores (2-10nm) and (3) the confinement and surface chemistry of different mesoporous metal 3D-nanowire networks.
The near neighbor effects were studied using nano-patterned Ag lines on Cu with varying spacing while keeping the effective ratio of catalytic area around 1 to 1. Nano-imprint lithography was selected as simple and versatile high-throughput nano-fabrication method for the co-catalyst systems. The systematic approach of bringing regular patterns of Ag closer to Cu sites allowed establishing electrode design guidelines for optimal coupling between reaction intermediates of these two co-catalysts to C2+ products. For the nano-confinement, initially the trapping of CO2RR reaction products inside a few nm small regular-arranged vertical mesopores of SiO2 was explored, but without the desired effect and it was concluded that confinement inside mesoporous oxide templates is not a straightforward methodology. As an alternative more promising concept, copper and silver 3D-nanowire networks (nanomeshes) that act directly as high surface area catalysts and nanoreactors were intensively studied within NANOconfine. The electrodes were fabricated by electrochemical plating in 3D-porous aluminium oxide templates in a similar manner as shown for nickel electrodes applied in alkaline-membrane water electrolysis by the MSCA fellow [1]. The effect of the surface chemistry and nano-confinement in governing the formation of CO2RR products on Ag and Cu nanomesh electrodes were investigated by Raman spectroscopy, online gas chromatography and electrochemical analysis in different electrolytes. It was found that the high surface area of the nanomesh primarily promotes the more catalytic reaction, i.e. with the lowest overpotential. On the Cu nanomesh the HER was preferentially enhanced with a reduction in overpotential of ~450mV, moving the potential even outside the window of some of the CO2RR products found at planar electrodes. On the Ag nanomesh, on the other hand, the CO2RR to CO was preferred over HER where the 250mV lowering of the overpotential for the same current density results in increased energy efficiency for CO2RR. These findings highlight the need to investigate whether the desired CO2RR or the competing HER will be enhanced by high surface area electrodes in relation to the nano-architecture and the catalysts nature as an important step forward towards upscaling the CO2RR electrolysis technology.
The encouraging results of NANOconfine were presented at several high impact international conferences in the field of materials electrochemistry and (electro)catalysis. The conference contribution on Cu 3D-nanowire networks for CO2RR was awarded the best oral presentation award at the e-MRS Fall Meeting 2021 and the MSCA fellow was invited to become a member of the scientific committee in the e-MRS Fall Meeting 2022 symposium on (photo)electrocatalytic materials. The research of NANOconfine has lead to 4 peer-reviewed publications in high impact and expert journals (Materials Today Energy, Angewandte Chemie, JES, Electrochimica Acta). The outstanding results on nanomesh electrodes for electrocatalytic applications were featured in several popular (online) magazines after an imec press release [2]. A wider public was reached through social media posts in researcher communities (e.g. ResearchGate [3]) and professional networking platforms such as LinkedIn [4].
[1] Materials Today Energy 2022, 30, 101172, https://doi.org/10.1016/j.mtener.2022.101172(opens in new window)
[2] https://www.imec-int.com/en/press/100-fold-current-density-enhancement-puts-imecs-nanomesh-electrodes-pole-position-high(opens in new window)
[3] https://www.researchgate.net/profile/Nina-Plankensteiner(opens in new window)
[4] https://www.linkedin.com/in/nina-winkler/?originalSubdomain=at(opens in new window)
The encouraging results of NANOconfine were presented at several high impact international conferences in the field of materials electrochemistry and (electro)catalysis. The conference contribution on Cu 3D-nanowire networks for CO2RR was awarded the best oral presentation award at the e-MRS Fall Meeting 2021 and the MSCA fellow was invited to become a member of the scientific committee in the e-MRS Fall Meeting 2022 symposium on (photo)electrocatalytic materials. The research of NANOconfine has lead to 4 peer-reviewed publications in high impact and expert journals (Materials Today Energy, Angewandte Chemie, JES, Electrochimica Acta). The outstanding results on nanomesh electrodes for electrocatalytic applications were featured in several popular (online) magazines after an imec press release [2]. A wider public was reached through social media posts in researcher communities (e.g. ResearchGate [3]) and professional networking platforms such as LinkedIn [4].
[1] Materials Today Energy 2022, 30, 101172, https://doi.org/10.1016/j.mtener.2022.101172(opens in new window)
[2] https://www.imec-int.com/en/press/100-fold-current-density-enhancement-puts-imecs-nanomesh-electrodes-pole-position-high(opens in new window)
[3] https://www.researchgate.net/profile/Nina-Plankensteiner(opens in new window)
[4] https://www.linkedin.com/in/nina-winkler/?originalSubdomain=at(opens in new window)
In electrocatalysis, the rational design of the catalyst electrode is often overlooked and nano-materials are often randomly distributed on porous host materials. This approach was shown to work mostly for CO2 reduction reactions were a low number of electrons transferred yield lower carbon reaction. However, to convert CO2 in economically more attractive chemicals such as C2+ oxygenates and hydrocarbons new strategies are needed. The fundamental insights in stirring the electrocatalytic CO2RR towards specific products shown in NANOconfine will help to deterministically design controlled reactions and exchange of intermediates in catalysts systems consisting of two co-catalysts and/or regular 3D-networks of catalysts. The findings of NANOconfine did therefore advance research on CO2 utilization and conversion through electrochemical approaches in the EU. The work done in the project fits well within R&D strategies of the host institute imec and the concepts shown in the project will be further developed towards high-throughput gas diffusion electrodes to enable large-scale industrial application of the CO2RR. With these prospects, the project is expected to have a large impact towards mitigating carbon emissions and generating economic return with innovative technologies in the EU.