Interstitial B-Doping in Pt Lattice to Upgrade Oxygen Electroreduction Performance

The dissolution of M in currently popular Pt–M alloy catalysts (M = Co, Ni, and Fe) during the oxygen reduction reaction (ORR) may deter their wide application in proton exchange membrane fuel cells (PEMFCs). In this work, interstitial B-doping in the Pt lattice is instead used to design a durable and active ORR catalyst, by taking advantage of its unique regulation of the electronic structure of surface Pt sites. 3 nm Pt–B nanoparticles on carbon black (Pt–B/C) are obtained using dimethylamine borane (DMAB) as a reductant and the B source in a mixed H2O–ethylene glycol precursor solution. The formation of the B-doped Pt catalyst is verified by inductively coupled plasma-atomic emission spectrometry, X-ray diffractometry, and spherical aberration-corrected scanning transmission electron microscopy. Both half-cell and single-cell tests indicate that the as-synthesized Pt–B/C catalyst outperforms the commercial Pt/C(com) in terms of activity and durability. In particular, the Pt–B/C-based PEMFC exhibits an initial maximum power density 1.24 times as high as the Pt/C(com)-based one under otherwise same conditions, with a 15% decay for the former versus a 45% decay for the latter after 30 000 cycles of the accelerated degradation test (ADT). Comparative DFT calculations on B-doped and undoped Pt(111) surfaces reveal that the lowered Pt d-band center and the strong interaction of Pt–B bonding weaken the binding of OH and O species to surface Pt sites and lessen oxidative disruption of surface Pt atoms. This interstitial metalloid doping in conjunction with the simple and scalable synthesis protocol enables the Pt–B/C to be a competitive ORR catalyst for the PEMFCs.