The cathode Pt-based electrocatalyst, a core component of high-temperature proton exchange membrane fuel cells (HT-PEMFCs), significantly influences fuel cell efficiency. At high temperatures and strongly acidic pH, phosphoric acid tends to adsorb onto the Pt surface by forming PtO bonds, covering the catalyst's active sites. Phosphoric acid anions' toxicity towards Pt significantly impairs the oxygen reduction reaction (ORR) kinetics, posing a major obstacle to the commercial viability of this technology. In this study, we activated the carbon layer by introducing boron (B) to anchor intermetallic compounds clusters, which competitively adsorb desorbed phosphate anions in HT-PEMFCs. This approach mitigates phosphoric acid poisoning. Additionally, the core-shell configuration induces compressive strain in PtMn intermetallic compounds, inhibits transition metal solvation, and regulates the d-band center, optimizing the adsorption energy of oxygen reduction intermediates and enhancing the catalyst's activity and stability in high-temperature phosphoric acid. At 80 °C, experiments showed the E