Developing highly active and durable catalysts with minimal platinum (Pt) usage is crucial for reducing the overall cost of proton exchange membrane fuel cells (PEMFCs). Herein, we introduce a scalable synthesis of carbon-bound catalysts using the upcycling of the polystyrene (PS) polymer. Our approach utilizes solvent-based hyper-cross-linking techniques to spontaneously achieve a hierarchically porous structure in a single-step process. The Pt-loaded PS-derived carbon support features a mesopore structure that enhances mass transport for PEMFCs, despite a low Pt loading of 0.05 mgPt cm–2. The catalyst exhibits excellent durability, retaining 92.1% of its initial power density after 30,000 cycles, owing to its carbon-bound structure and the strong interaction between catalyst and support. In contrast, the power density of commercial Pt/C retains only 35.8% after 30,000 cycles. This approach offers a cost-efficient and sustainable method for upcycling PS polymers into highly durable cathode materials for PEMFCs.