Regulating orbital interaction to construct quasi-covalent bond networks in Pt intermetallic alloys for high-performance fuel cells
Xuan Liu, Yuhan Wang, Hu He, Zhonglong Zhao, Xuan Luo, Siyang Zhang, Gang Lu, Dong Su, Yucheng Wang, Yunhui Huang, Qing Li, Yunhui Huang, Qing Li
Abstract
The long-standing challenges facing Pt-based alloy catalysts in oxygen reduction reactions (ORRs) are rapid oxidation and loss of transition metal/Pt in proton exchange membrane fuel cells (PEMFCs). In this work, we report a concept of “covalentization” in intermetallic L10-PtMM’ (M = Fe, Co, Ni and M’ = one of the 4th-period elements (from Ti to Ge)) alloys to enhance their electrochemical stability. Specifically, the formation of a quasi-covalent bond network in L10-PtMM’ due to the less occupied antibonding states induced by high d-band positions of M’ elements (e.g., Ti, V, Cr) enhances atomic bond order and strength, diminishing Co anodic dissolution via strengthened Pt/Co-M’ bonds and reducing Co cathodic corrosion by inhibiting Pt oxidation through an electron buffering effect. The developed L10-PtCoCr/C catalysts show a high mass activity (MA = 1.27 A mgPt−1) and rated power (16.5 W mgPt−1) in PEMFCs at a low total Pt loading of 0.075 mgPt cm−2. The catalysts also exhibit high electrochemical stability with ~3% and 5% loss of MA and rated power after 30,000 accelerated durability testing cycles and projects a lifetime of about 42,000 hours. Pt-based alloy cathode catalysts in proton exchange membrane fuel cells face persistent challenges, including rapid oxidation and loss of transition metal/Pt. Here, the authors report a covalentization concept in intermetallic L10-structure Pt-based alloys to boost stability in fuel cells.