Robust Oxygen-Reduction Electrocatalyst Scaffold for High-Temperature Phosphoric Acid Fuel Cells Using Tailored...

The work is motivated by lack of durable catalyst supports for high-temperature phosphoric acid fuel cells and demonstrates that a robust, tailored, nanoporous, partially graphitic carbon spherules scaffold can deliver high activity, stability, and efficient electron transport under harsh operating conditions. Carbon spherules (360-380 nm) are synthesized via a silica-templating route and heat treated to optimize carbon stacking and graphitic order to engineer a stable scaffold suitable for high-temperature and high-voltage fuel cell applications. Key characteristics like surface area, pore volume, pore size, and corrosion resistance are systematically optimized. Initially carbonized at 1173 K, the spherules are further heat-treated at 1773 and 2773 K to yield three carbon scaffolds: MCHT900, MCHT1500, and MCHT2500. These scaffolds are comprehensively characterized using appropriate spectroscopic and microscopic techniques, along with surface area analysis, density measurements, and chronoamperometric studies under constant potential conditions. A holistic approach involving three levels of experimentation, namely, powder level, catalyst level, and gas diffusion electrode level, is adopted to progressively screen and identify the most promising scaffold. This multistage evaluation ensures that only most qualified and competent scaffold is selected, while the less effective candidates are eliminated at each stage. Results from these multiple layers of scrutiny indicate that MCHT1500 holds strong promise as a durable and suitable electrocatalyst scaffold for fuel cell applications. A catalyst comprising 20 wt % Pt loaded on MCHT1500 is evaluated at two stages: the catalyst powder level and the catalyst-coated electrode level. 20 wt %Pt on MCHT1500 demonstrates significant potential as an electrocatalyst, exhibiting both excellent oxygen reduction reaction activity and enhanced stability. Electrode-level efficiency is assessed by a catalyst-coated gas diffusion electrode. Testing a unit cell equipped with a 20 wt % Pt on MCHT1500 catalyst-coated gas diffusion electrode in a phosphoric acid environment reveals strong potential for its application in phosphoric acid fuel cells.