Periodic Reporting for period 1 - ADBCRZB (Atomically Dispersed Bifunctional Catalysts for Reversible Zn-CO2 Batteries)
Reporting period: 2020-10-01 to 2022-09-30
From the material point of view. This project has developed two types of cooperative SACs, including Cu-Sn single-atom alloys and Ni-N-C single-atom catalysts, to overcome the performance limits set by the scaling relationship for energy-efficient and selective electrochemical CO2 conversion at industrial-relevant currents. From the mechanism point of view. This project has combined in situ Raman, density function theory simulation, and electrochemical analysis to reveal the reaction pathways and adsorption of intermediates during CO2 conversion, which shed some light for the understanding of CO2 conversion mechanism at single atom limit. From a device point of view. This project has further integrated the SACs into practical membrane electrode assembly full cell, and achieved the state-of-the-art energy efficiency for both CO and formate production.
The design and manufacture of cost-effective, safe, and reliable electrochemical CO2 conversion systems are essential to meet current escalating energy demands and mitigate climate change. This project has made substantial improvements to electrochemical CO2 reduction, so they provide higher energy efficiencies (voltages), superior selectivity, and longer service life. Based on these metrics, this technology can potentially provide a cell prototype to store intermittent renewable energy (e.g. solar, wind, and water power) into valuable products (e.g. CO, formate, C2H4), which can be incorporated into grid-scale energy storage systems. New energy storage systems will also offer more flexible, cheap, and efficient energy use for consumers.
Overall, the project has achieved the major objectives and milestones for the period, including the development of new single-atom catalysts, the corresponding mechanistic investigations in CO2 conversion, and the development of energy-efficient membrane electrode assembly full cells for CO2 conversion.
The design and manufacture of cost-effective, safe, and reliable electrochemical CO2 conversion systems are essential to meet current escalating energy demands and mitigate climate change. This project has made substantial improvements to electrochemical CO2 reduction, so they provide higher energy efficiencies (voltages), superior selectivity, and longer service life. Based on these metrics, this technology can potentially provide a cell prototype to store intermittent renewable energy (e.g. solar, wind, and water power) into valuable products (e.g. CO, formate, C2H4), which can be incorporated into grid-scale energy storage systems. New energy storage systems will also offer more flexible, cheap, and efficient energy use for consumers.
Overall, the project has achieved the major objectives and milestones for the period, including the development of new single-atom catalysts, the corresponding mechanistic investigations in CO2 conversion, and the development of energy-efficient membrane electrode assembly full cells for CO2 conversion.
1. Design and development of cooperative single-atom catalysts.
(i) Cu–Sn single-atom surface alloys, where isolated Sn sites with high surface densities (up to 8%) are anchored on the Cu host, have been developed. (ii) A densely populated Ni single-atom on nanoparticle catalyst via direct solid-state pyrolysis has been synthesized. A series of powerful tools have been used to reveal the atomic structure of the single atom catalysts, including atom probe tomography, x-ray absorption spectroscopy, transmission electron microscopy, etc. Afterward, the synthesized samples were subjected to electrochemical testing such as linear sweep voltammetry (LSV) and constant voltage to determine the optimal elemental composition and single atom loading for the best CO2 electroredcution activity and selectivity.
2. Mechanistic investigations of the catalyst cathodes.
The mechanistic for electrochemical CO2 conversion has been investigated by the combination of in situ Raman, electrochemical analysis (e.g. ECSA, EIS, Tafel, etc.), and density functional theory simulations. In this way, the reaction pathways and adsorbed intermediates for CO2 conversion have been further understood. A general electronic tuning effect is observed for the cooperative single-atom catalysts, which can regulate the binding strength between active sites and intermediates, and breaks the performance limits set by the scaling relationship.
3. Development, characterisation, and optimisation of CO2-based full cells
To fabricate full cells based on electrochemical CO2 conversion. Three strategies have been explored for cell-level optimisation, including the use of gas diffusion electrode (GDE), the membrane electrode assembly (MEA) design, and the development of a strong acidic system. For Cu–Sn single-atom alloys, a CO Faradaic efficiency of 98% at a tiny overpotential of 30 mV in an alkaline flow cell has been achieved. For Ni single-atom catalysts, it delivers an industrial-relevant CO current of 310 mA cm−2 at a low cell voltage of -2.3 V, corresponding to an overall ultra-high energy efficiency of 57%. Besides, a high Faradaic efficiency for formic acid and CO production has been achieved in a strong acid system based on the cation effect, which can solve the carbonate issue in near-neutral and alkaline conditions.
These findings suggest that the development of cooperative SACs is effective for tuning the property of single-atom-sites through the atomic interactions, and subsequently modulating the CO2 reduction pathways. The well-defined active sites in SACs can provide an ideal model for mechanistic studies and enable the rational construction of catalysts through a three-pronged approach, comprising operando characterisations, theoretical modelling, and catalyst assessment under industrially relevant conditions.
We have published the research results of this project through world-leading peer-reviewed journals as either gold open access or green open access (with the deposition of publications in open access repositories) articles. I have attended two conferences, including 1. 2022 Renewable Energy: Solar Fuels Gordon Research Conference, Lucca (Barga), LU, Italy, May 8 - 13, 2022, (Poster presentation). 2. CUHK-Shenzhen 2022 Long Feng Science Forum, online Zoom meeting, August 19 - 21, 2022, (Oral presentation). In all the cases, a reference to EU funding was included.
(i) Cu–Sn single-atom surface alloys, where isolated Sn sites with high surface densities (up to 8%) are anchored on the Cu host, have been developed. (ii) A densely populated Ni single-atom on nanoparticle catalyst via direct solid-state pyrolysis has been synthesized. A series of powerful tools have been used to reveal the atomic structure of the single atom catalysts, including atom probe tomography, x-ray absorption spectroscopy, transmission electron microscopy, etc. Afterward, the synthesized samples were subjected to electrochemical testing such as linear sweep voltammetry (LSV) and constant voltage to determine the optimal elemental composition and single atom loading for the best CO2 electroredcution activity and selectivity.
2. Mechanistic investigations of the catalyst cathodes.
The mechanistic for electrochemical CO2 conversion has been investigated by the combination of in situ Raman, electrochemical analysis (e.g. ECSA, EIS, Tafel, etc.), and density functional theory simulations. In this way, the reaction pathways and adsorbed intermediates for CO2 conversion have been further understood. A general electronic tuning effect is observed for the cooperative single-atom catalysts, which can regulate the binding strength between active sites and intermediates, and breaks the performance limits set by the scaling relationship.
3. Development, characterisation, and optimisation of CO2-based full cells
To fabricate full cells based on electrochemical CO2 conversion. Three strategies have been explored for cell-level optimisation, including the use of gas diffusion electrode (GDE), the membrane electrode assembly (MEA) design, and the development of a strong acidic system. For Cu–Sn single-atom alloys, a CO Faradaic efficiency of 98% at a tiny overpotential of 30 mV in an alkaline flow cell has been achieved. For Ni single-atom catalysts, it delivers an industrial-relevant CO current of 310 mA cm−2 at a low cell voltage of -2.3 V, corresponding to an overall ultra-high energy efficiency of 57%. Besides, a high Faradaic efficiency for formic acid and CO production has been achieved in a strong acid system based on the cation effect, which can solve the carbonate issue in near-neutral and alkaline conditions.
These findings suggest that the development of cooperative SACs is effective for tuning the property of single-atom-sites through the atomic interactions, and subsequently modulating the CO2 reduction pathways. The well-defined active sites in SACs can provide an ideal model for mechanistic studies and enable the rational construction of catalysts through a three-pronged approach, comprising operando characterisations, theoretical modelling, and catalyst assessment under industrially relevant conditions.
We have published the research results of this project through world-leading peer-reviewed journals as either gold open access or green open access (with the deposition of publications in open access repositories) articles. I have attended two conferences, including 1. 2022 Renewable Energy: Solar Fuels Gordon Research Conference, Lucca (Barga), LU, Italy, May 8 - 13, 2022, (Poster presentation). 2. CUHK-Shenzhen 2022 Long Feng Science Forum, online Zoom meeting, August 19 - 21, 2022, (Oral presentation). In all the cases, a reference to EU funding was included.
1. The design and synthesis of single-atom catalysts is a cutting-edge area of research, and the study of cooperative catalysts remains an emerging field. In this project, the candidate has developed a toolbox for the controllable synthesis of a class of cooperative SACs, which can potentially go beyond the state-of-the-art and provide a deterministic approach to accessing the atom catalysts. In addition, the new catalysts design strategy acquired in this project can also be potentially utilised in other fields such as Zn-air battery, Li-CO2 battery, OER/ORR, N2 fixation, etc. 2. As high time-resolution techniques, spectroscopic characterisations such as Raman is important for the direct observation of absorbed intermediates (M-C, CO2*, CO*, H2O, etc.), which is critical for determining the reaction pathways. Based on in situ Raman, this project has provided new and in-depth insights into mechanistic studies, enabling the rational construction of catalysts through a three-pronged approach, comprising operando characterisations, theoretical modelling, and catalyst assessment under industrially relevant conditions. 3. Electrochemical CO2 reduction offers a promising route to convert greenhouse gas into high-value chemicals, meanwhile storing renewable but intermittent electricity. However, the intrinsic carbonate issue caused by the reaction between CO2 and in situ generated OH- results in low carbon efficiency (CO2-to-products) and precipitate problem (e.g. KHCO3/K2CO3), making it unsustainable for long-term operation with low energy efficiency. This project has developed a strong acidic system to tackle the carbonate issue, meanwhile maintaining efficient CO2 reduction based on the cation effect. The general feasibility of this strong acidic system has been demonstrated on Cu, Au, and Sn-based catalysts for various products (e.g. CO, formate, etc.) fabrication. This new acidic system is thus promising for sustainable CO2 conversion that goes beyond the state-of-the-art near-neutral or alkaline conditions.