The development of highly active and durable platinum‐free oxygen reduction reaction (ORR) catalysts is of vital importance for the practical application of anion‐exchange membrane fuel cells (AEMFCs). Herein, a metal‐free carbon catalyst (marked as NDPC‐1000) with a graphitic N‐regulating defect structure is specifically designed and developed for AEMFCs by integrating theoretical calculations and experiments. Density functional theory calculations first reveal that the graphitic N can tailor the charge density of pentagon and armchair defects to reach the top of the adsorption energy‐activity volcano plot, while the enhanced durability is attributed to the high dissociation energy of the CN covalent bond. Under this guidance, the synthesized NDPC‐1000 demonstrates its high ORR activity and durability in alkaline media. With H2/O2 reacting gases, the AEMFC with this catalyst as the cathode delivers a peak power density of 913 mW cm−2. Unprecedented fuel cell durability is verified via continuous operation over 100 h at 0.25 A cm−2 with only a voltage decay of ≈25%, which is the greatest among all reported metal‐free‐based AEMFCs. Here a theory‐guided experiment strategy is provided for the development of high‐performance and durable ORR catalysts for AEMFCs.
Regulating the p-orbital valence electrons of atomically dispersed main-group metals to improve the inherent electrocatalytic activity has attracted extensive concerns. Herein, we designed and synthesized an atomically dispersed Sb−SeNC catalyst containing SbN 2 C 2 and SeC 2 structures, which have been identified by X-ray absorption spectroscopy and density functional theory (DFT) calculations. Sb−SeNC exhibits a high activity for the oxygen reduction reaction (ORR), and a Sb− SeNC-based flexible solid-state zinc−air battery (ZAB) can work efficiently at −40 °C, with a peak power density of 54.1 mW cm −2 and a rate discharge operation of about 44 h. DFT calculations further confirm the long-range regulation mechanism of the SeC 2 moiety for the ORR of SbN 2 C 2 and obtain the volcano relationship of U onset vs the Se−N distance. When the Se−N distance is 7.4 Å, the adsorption ability of active site Sb can be regulated to an optimal state related to the RDS: *O → *OH, while the smaller Se−N distance in short-range would lead to the excessive attenuation of adsorption ability of active site and decrease of ORR activity, which therefore yields the long-range regulation effect of Se doping on the ORR activity of SbN 2 C 2 . This long-range regulation strategy may provide a promising approach to boost the catalytic activity of main-group metal catalysts to achieve its application in ultralow-temperature solid-state ZABs.
Discovering highly efficient and stable non-precious
metal catalysts
for the oxygen evolution reaction (OER) is crucial for energy conversion
in water splitting. However, preparing high-performance OER catalysts
and elucidating the structural changes in the process are still challenging.
Herein, we synthesize the NiTe/Ni2P heterostructure and
demonstrate the strain engineering of NiTe/Ni2P via the
lattice incompatibility between the phosphide and the telluride. The
strain engineering of the NiTe/Ni2P heterostructure not
only significantly boosts the OER activity but also effectively stabilizes
the intrinsic structure of the catalyst after the OER process by using
the in situ-produced metal salt as a protection layer.
After the OER stability test, no oxyhydroxide phase is observed, and in situ Raman spectroscopy reveals that a voltage-dependent
phase transition appears during the OER, which is different from most
previously reported Ni-based catalysts, for which the generation of
irreversible NiOOH occurs after the OER. Density functional theory
calculations further reveal that the tensile strain of Ni2P will inhibit the presence of irreversible phase transitions of
Ni2P into NiOOH due to the weak adsorption ability of the
oxygen species caused by strain engineering. In short, this work opens
a new gate for using strain nanotechnology to design high-performance
OER catalysts.
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