Phosphoric acid resistance PtCu/C oxygen reduction reaction electrocatalyst for HT-PEMFCs: A theoretical and experimental study

Abstract

In high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), dissociative H3PO4 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 H3PO4 poisoning are significantly important. Due to the similar bonding structure between HxPO43-x/O2 and Pt (Pt-O), the design of catalysts which could selectively reduce the adsorption energy of the H3PO4 is urgently needed. In this work, we screen proper H3PO4 resistance electrocatalysts through theoretical calculation based on the adsorption energy difference between HxPO43-x and O2 as an evaluation criterion. Then, we prepared a series of PtxCu 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 Pt2Cu/C is 0.51 A/mgPt, exceeding the DOE's 2020 target of 0.44 A/mgPt. After add 0.1 M H3PO4 into the HClO4 electrolyte, the half-wave potential (E1/2) of Pt2Cu/C is only negatively shifted by 47 mV, much lower than 90 mV of TKK Pt/C. Furthermore, the HT-PEMFC with Pt2Cu/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.