Competitive adsorption and strain modulation induced by low electronegative elements to improve phosphate tolerance in HT-PEMFC

Abstract

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_1/2 value of PtMn/BC was 0.854 V, 53 mV higher than commercial Pt/C. Additionally, the mass activity (MA) and specific activity (SA) were 5.2 and 2.6 times higher than those of commercial Pt/C, respectively. The maximum power density of the HT-PEMFC in an H₂/O₂ atmosphere reached 1108.3 mW cm⁻², significantly higher than that of commercial Pt/C. This value is also higher than most reported ORR catalysts, demonstrating the potential of this catalyst for HT-PEMFC applications.