Understanding the Rheological Insights for Scalable Fabrication of Catalyst-Embedded Carbon Fibers—Exsolution-Driven Structural Development During Carbonization

The urgent demand for sustainable energy solutions has propelled the development of efficient and stable electrochemical catalysts for hydrogen production via water splitting. While metal-carbon nanocomposite powders have shown promise as electrocatalysts, their scalable fabrication and long-term stability remain significant challenges. The use of polymeric binders to coat these catalysts on electrodes can mask electroactive sites, hinder electron transfer, and cause peeling under high current densities. To address these issues, recent research has focused on designing self-supported catalysts, with carbon fiber-based materials receiving particular attention due to their excellent mechanical properties, high surface area, and good electrical conductivity. However, current approaches suffer from poor interfacial adhesion and limited scalability, necessitating the development of cost-effective and scalable manufacturing routes for high-performance electrocatalytic electrodes.<br/>In this study, we present a comprehensive investigation of the rheological properties and exsolution-driven structural development mechanisms to enable the scalable fabrication of ruthenium-embedded carbon fiber electrocatalysts. By elucidating the rheological behavior of the catalyst-containing precursor solution, we optimized the coating process to achieve a uniform distribution of ruthenium nanoparticles around the carbon fibers, overcoming the challenges posed by increased Laplace pressure on the curved fiber surfaces.<br/>Furthermore, we systematically investigated the exsolution-driven microstructural development of the ruthenium-embedded carbon fiber electrocatalysts during the carbonization process. This was achieved by understanding the exsolution mechanisms with respect to the processing parameters, including carbonization temperature and tension, and optimizing the structural development to achieve good catalytic performance and mechanical integrity. These findings underscore the significance of self-supporting catalysts, offering a general framework for stable, self-supported electrocatalytic electrode design.<br/>The insights gained from this study allowed us to optimize the carbonization conditions to achieve the desired catalytic activity and stability. The scalability of our approach was demonstrated using semipilot-scale equipment, where we established a highly optimized protocol for producing continuous self-supported electrocatalytic electrodes. The resulting electrodes exhibited excellent catalytic activity and stability towards the hydrogen evolution reaction, with a low overpotential of 11.9 mV at a current density of 10 mA cm^-2 in an alkaline solution and only a slight overpotential increment (6.5%) after 10,000 cycles.<br/>Our findings underscore the importance of understanding the rheological properties and exsolution-driven structural development mechanisms in the scalable fabrication of high-performance catalyst-embedded carbon fiber electrocatalysts. This work provides a general framework for the design and manufacture of stable, self-supported electrocatalytic electrodes for various energy conversion applications.