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The H3PO4 poisoning problem severely limits the performance of high‐temperature proton exchange membrane fuel cells (HT‐PEMFCs) using the H3PO4‐doped polybenzimidazole as electrolyte membrane. Herein, the micropore‐rich carbon shell‐confined Pt‐based nanoparticles (Pt@MPC) with a Pt loading of 44.9 wt% is developed as the H3PO4 poisoning‐resistant electrocatalyst for oxygen reduction reaction (ORR), which possesses both high ORR activity and stability. The half‐wave potential (E1/2) of 0.898 V and electrochemical active surface area (ECSA) of 62.3 m2 gPt−1 are superior to commercial 40 wt% Pt/C (E1/2 = 0.892 V; ECSA = 53.1 m2 gPt−1). Pt@MPC remains almost unchanged after the accelerated durability test of 10 000 cycles. Moreover, Pt@MPC exhibits remarkable H3PO4 tolerance as its negative shift of E1/2 (82 mV) is less in H3PO4‐containing electrolyte compared with commercial Pt/C (114 mV). This can be attributed to the steric effect of the micropore‐rich carbon, which enables the selective transport of reactants while inhibiting H3PO4. The HT‐PEMFCs assembled with Pt@MPC (0.7 mgPt cm−2) exhibit a maximum power density of 674 mW cm−2 under the H2‐O2 condition and outperform the commercial Pt/C (616 mW cm−2). This strategy provides a new direction for the design of ORR catalysts toward HT‐PEMFCs with better phosphoric acid poisoning resistance. [ABSTRACT FROM AUTHOR]

Phosphoric acid (PA), utilized as an electrolyte in high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), has been observed to exert a detrimental effect on oxygen reduction reaction (ORR) electrocatalyst, consequently compromising cell performance. To comprehensively elucidate the impact of phosphoric acid on ORR, this study employs a range of electrochemical techniques, including electrochemical impedance spectroscopy and voltammetry method. The negative influence of PA on commercial Pt/C electrocatalyst manifests differently under various potentials and PA concentrations. Upon the introduction of PA, the decay rate and amplitude of ECSA, as calculated by H upd adatoms, are notably smaller compared to the kinetic current density generated by the oxygen reduction reaction. Particularly, in the kinetic-controlled potential range, the negative impact of PA becomes more pronounced at higher electrode potentials, accompanied by a significantly steeper Tafel slope. Additionally, the EIS results suggest that phosphoric acid may gradually transform into polyphosphoric acid at a high concentration, accentuating the poisoning effect of PA under steady-state conditions. However, a high PA concentration can substantially alter the electrolyte properties, potentially leading to an inaccurate assessment of PA tolerance in electrocatalysts. Hence, it is imperative to consider the appropriate PA concentration when evaluating PA tolerance and to discern the poisoning mechanism under different electrode potentials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Design of the prior PA-resistance electrocatalysts through theoretical calculation. • Discovery of different scaling relationship of the adsorption energy difference of O 2 and H x PO(3-x)- 4 on Pt 3 M(1 1 1) alloy surface. • Pt X Cu as the object for the research of internal mechanism of the potentially high PA resistance property. • Higher PA-resistance performance of Pt 2 Cu compared to the commercial PtC in half-cell and full-cell tests. In high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), dissociative H 3 PO 4 in cathode will block the active sites of Pt-based electrocatalyst, which thus failure to catalyze the oxygen reduction reaction (ORR). Therefore, the electrocatalysts for the ORR in HT-PEMFCs with high resistance to H 3 PO 4 poisoning are significantly important. Due to the similar bonding structure between H x PO 4 3-x/O 2 and Pt (Pt-O), the design of catalysts which could selectively reduce the adsorption energy of the H 3 PO 4 is urgently needed. In this work, we screen proper H 3 PO 4 resistance electrocatalysts through theoretical calculation based on the adsorption energy difference between H x PO 4 3-x and O 2 as an evaluation criterion. Then, we prepared a series of Pt x Cu catalysts based on the theoretical calculation results and further studied the structure-performance relationship of phosphoric acid-resistant catalysts through combining physical property characterization and electrochemical tests including half-cell and single-cell. The mass activity of Pt 2 Cu/C is 0.51 A/mg Pt , exceeding the DOE's 2020 target of 0.44 A/mg Pt. After add 0.1 M H 3 PO 4 into the HClO 4 electrolyte, the half-wave potential (E 1/2) of Pt 2 Cu/C is only negatively shifted by 47 mV, much lower than 90 mV of TKK Pt/C. Furthermore, the HT-PEMFC with Pt 2 Cu/C in the cathode shows a peak power density of 383.4 mW/cm2, which surpasses that of TKK Pt/C for 231.0 mW/cm2. Our strategy of screening catalysts based on the adsorption energy difference study and further verified by experimental methods provides a promising strategy for the design of practical electrocatalyst in the cathode of HT-PEMFCs. [ABSTRACT FROM AUTHOR]