posted on 2023-11-14, 05:29authored byFan Liu, Ruijie Gao, Chengxiang Shi, Lun Pan, Zhen-Feng Huang, Xiangwen Zhang, Ji-Jun Zou
The
development of highly active and low-cost oxygen reduction
reaction (ORR) catalysts is crucial for the practical application
of hydrogen fuel cells. However, the linear scaling relation (LSR)
imposes an inherent Sabatier’s limitation for most catalysts
including the benchmark Pt with an insurmountable overpotential ceiling,
impeding the development of efficient electrocatalysts. To avoid such
a limitation, using earth-abundant metal oxides with different crystal
phases as model materials, we propose an effective and dynamic reaction
pathway through constructing spatially correlated Pt–Mn pair
sites, achieving an excellent balance between high activity and low
Pt loading. Experimental and theoretical calculations demonstrate
that manipulating the intermetallic distance and charge distribution
of Pt–Mn pairs can effectively promote O–O bond cleavage
at these sites through a bridge configuration, circumventing the formation
of *OOH intermediates. Meanwhile, the dynamic adsorption configuration
transition from the bridge configuration of O2 to the end-on
configuration of *OH improves *OH desorption at the Mn site within
such pairs, thereby avoiding Sabatier’s limitation. The well-designed
Pt–Mn/β-MnO2 exhibits outstanding ORR activity
and stability with a half-wave potential of 0.93 V and barely any
activity degradation for 70 h. When applied to the cathode of a H2–O2 anion-exchange membrane fuel cell, this
catalyst demonstrates a high peak power density of 287 mW cm–2 and 500 h of stability under a cell voltage of 0.6 V. This work
reveals the adaptive bonding interactions of atomic pair sites with
multiple reactant/intermediates, offering a new avenue for rational
design of highly efficient atomic-level dispersed ORR catalysts beyond
the Sabatier optimum.