At 3:00 Beijing time on February 14, the research results of the collaborative team of Bo Zhang, Yifei Xu, Sai Duan and Xin Xu from Fudan University were published in the main issue of Science under the title of 'Ultrastable supported oxygen evolution electrocatalyst formed by ripening induced embedding' was published in the main issue of Science. Wenjuan Shi, a full-time associate researcher at the Department of Polymer Science, Fudan University (member of Bo Zhang's team), and Tonghao Shen, a full-time associate researcher at the Department of Chemistry (member of Xin Xu's team), were the co-first authors of the paper.
The paper designed an embedded catalyst with Ir metal particles embedded on the surface of CeO2 carrier to solve the problems of catalyst activity and stability in water electrolysis reaction.
Firstly, computational simulations were carried out by Xin Xu's team to determine the experimental conditions for matching the growth rates of the CeO2 carrier and the Ir particles on the surface. The reaction was challenging as it involved nearly a million atoms, while the synthesis process took up to three hours. Even with state-of-the-art machine learning accelerated molecular dynamics methods, utilising 30,000 CPUs and 30,000 GPUs, it would still take about 4.5 years to achieve. Therefore completely new algorithms must be developed for simulation. Using the idea of ‘separation of fast and slow processes’ originated by Xu Xin's team, the theoretical computation team adopted the Monte Carlo method of all-atom dynamics, repeatedly adjusted the idea and optimised the algorithm, and finally realised the simulation of a synthesis process within one hour on a single CPU computer, which provided quantitative theoretical analysis for mapping the experimental conditions.
Theoretical simulations show that the embedding of metal particles on the carrier surface can only be achieved by maintaining the continuous growth of high-energy crystalline surfaces, in which matching the carrier growth rate and metal nucleation rate is the key. Based on this theoretical understanding, the experimental research team used ultrasound and heating together to greatly accelerate the spontaneous growth (ripening) of the nanocrystals and construct the matching relationship predicted by theory. In order to make the catalyst synthesis and growth process ‘seeing is believing’, the experimental research team used cryo-transmission electron microscopy (CryoTEM) and cryo-electron tomography (CryoET) to clearly see the growth and embedding of Ir particles through the time-resolved synthesis process. The observed results are in perfect agreement with the simulation results of the all-atom kinetic Monte Carlo (KMC) method, confirming the match between the carrier growth and catalyst nucleation rates and proving the validity of the synthesis strategy.
Using the synthesised embedded catalysts, the experimental research team conducted PEMWE working condition tests for up to 6000 hours. The results showed that the embedded catalyst effectively prevented the dissolution, detachment and agglomeration of iridium particles, which significantly improved the activity and stability of the catalyst in long-term operation. Under operating current density (3 A/cm2), the battery voltage using the catalyst was as low as 1.72 V, the voltage decay rate was only 1.3 μV/h, and the total precious metal loading was only 0.4 g/cm2, which comprehensively exceeded the relevant international standards (e.g., the US National Energy Administration 2026 design standards). Based on the experimental results, the lifetime of the PEMWE device thus prepared is estimated to be more than 15 years. These results demonstrate the feasibility of the embedded catalyst design strategy.
Theoretical studies point out that this synthetic embedded catalyst design strategy is universal. To verify this, the experimental team successfully synthesised a series of embedded catalysts including Ir/ZrOx, Pt/CeOx, Ru/TiOx and other metal-oxide combinations by controlling the matching of carrier growth and metal nucleation rate, which opens up a completely new path for the synthesis of stable catalysts.
Link to the paper: https://www.science.org/doi/10.1126/science.adr3149
