Periodic Reporting for period 3 - 123STABLE (Towards Nanostructured Electrocatalysts with Superior Stability)
Reporting period: 2023-01-01 to 2024-06-30
ERC Starting Grant 123STABLE is addressing the problem of unstable energy conversion fuel cells and electrolyzers. Especially, in their core component, namely electrocatalyst, the fundamental understanding of its long-term performance stability is not yet sufficient. Due to the scarcity and limited access to platinum and iridium, which are essential for these applications and at the same time also critical raw materials, we need to optimally utilize them to enable hydrogen economy technologies to become effective and economically viable. This is important for society as hydrogen economy provides the solution to completely replace fossil fuels and thus resolve global warming and eliminate the pollution it is causing. Fuel cells and electrolyzers possess enormous potential for converting and storing the harvested energy from the sun (wind) in a completely sustainable way. Although the technology is well known and already commercialized in some applications like cars, it still possesses a lot of space for improvement and further development. The aim of the 1234STABLE project is to obtain new insights into noble metals' atomic-scale corrosion and use this knowledge to design and produce new and improved metallic nanostructures with superior stability.
In the first half of the project, most of the work focused on establishing the methodology (schematically represented in the attached image) and using advanced characterization approaches to study Pt- and Ir-based electrocatalysts. Specifically, methodologies for preparing various electrocatalysts were established, covering different Pt- and Ir-alloy nanoparticles with diverse dopants, decorations, sizes, and supports (Pavko et al., ACS Appl. Energy Mater. 2021). Additionally, the identical location transmission electron microscopy approach was enhanced to achieve high current densities and atomic resolutions for both Pt-based (Hrnjić et al., Electrochim. Acta 2021) and Ir-based samples (Bele et al., ACS Applied Nano Materials 2023). Experimental methods and protocols were also developed to measure online dissolution and detect volatile species via mass spectroscopy (Moriau et al., Electrochimica Acta 2024; Pavko et al., Carbon 2023). Further upgrades are planned to make the experimental setup even more efficient.
In the paper by Đukić et al., ACS Catalysis 2021, the online dissolution setup was upgraded to include temperature control. Interestingly, increasing the temperature during electrochemical testing of our PtCo/C catalyst revealed that while Co dissolution increased, Pt dissolution decreased. These findings were expanded in a second paper by Đukić et al., ACS Catalysis 2024, demonstrating that Pt dissolution can be minimized by adjusting the operational potential window. Progress was also made in electron microscopy data processing and simulations as part of work package 2 (Koderman Podboršek et al., Electrochim. Acta 2022). We demonstrated the capability to automatically process atomically resolved STEM images using in-house developed algorithms, extracting unprecedented information such as surface roughening, which increased through electrochemical treatment of Ir nanoparticles larger than 2 nm, while it remained constant for smaller ones. We believe this approach will reveal new atomically-resolved insights into catalyst stability in other electrocatalytic systems. Recently, we successfully introduced the use of a new powerful detector, 4DSTEM, into the identical location TEM concept (Hrnjić et al., Electrochim. Acta 2024).
For work package 3, the initial results showed promising Pt-based electrocatalysts with enhanced stability, already produced on a large scale (Pavko et al., ACS Catalysis 2022). We published two new papers showing increased stability by changing the support of Pt-based nanoparticles to reduced graphene oxide (Pavko et al., Carbon 2023) and titanium oxynitride (Hrnjić et al., Electrochim. Acta 2024). Currently, we are testing more Pt catalysts with different electrochemical cells (RDE, GDE, and MEA) and developing methods to produce Ir-based catalysts on a larger scale, followed by testing in various electrochemical cells.
In the paper by Đukić et al., ACS Catalysis 2021, the online dissolution setup was upgraded to include temperature control. Interestingly, increasing the temperature during electrochemical testing of our PtCo/C catalyst revealed that while Co dissolution increased, Pt dissolution decreased. These findings were expanded in a second paper by Đukić et al., ACS Catalysis 2024, demonstrating that Pt dissolution can be minimized by adjusting the operational potential window. Progress was also made in electron microscopy data processing and simulations as part of work package 2 (Koderman Podboršek et al., Electrochim. Acta 2022). We demonstrated the capability to automatically process atomically resolved STEM images using in-house developed algorithms, extracting unprecedented information such as surface roughening, which increased through electrochemical treatment of Ir nanoparticles larger than 2 nm, while it remained constant for smaller ones. We believe this approach will reveal new atomically-resolved insights into catalyst stability in other electrocatalytic systems. Recently, we successfully introduced the use of a new powerful detector, 4DSTEM, into the identical location TEM concept (Hrnjić et al., Electrochim. Acta 2024).
For work package 3, the initial results showed promising Pt-based electrocatalysts with enhanced stability, already produced on a large scale (Pavko et al., ACS Catalysis 2022). We published two new papers showing increased stability by changing the support of Pt-based nanoparticles to reduced graphene oxide (Pavko et al., Carbon 2023) and titanium oxynitride (Hrnjić et al., Electrochim. Acta 2024). Currently, we are testing more Pt catalysts with different electrochemical cells (RDE, GDE, and MEA) and developing methods to produce Ir-based catalysts on a larger scale, followed by testing in various electrochemical cells.
Our new advanced characterization methodology platform has enabled us to go beyond the state-of-the-art in an understanding of Pt- and Ir-based electrocatalysts. Utilizing our unique approach, we are uncovering unprecedented insights into nanoparticulate electrocatalyst degradation mechanisms. We have prepared and are testing various new catalyst variations. Our capability to produce multi-gram batches allows us to conduct tests in real fuel cells and electrolyzers. Following the success of our new methodology, synthesis procedures, and in-house data processing algorithms, we have published several high-impact papers in the past year, with more forthcoming.