posted on 2024-01-24, 12:03authored byQianglong Qi, Yue Zhang, Chengxu Zhang, Feng Liu, Rongjiang Liu, Jue Hu
Iron-based metal–organic frameworks (MOFs) have
shown potential
as catalysts for the electrocatalysis oxygen evolution reaction (OER).
Despite numerous methods being employed to enhance the OER performance
of MOFs, the influence of halogen-containing linkers on the electronic
structure of iron-based MOF catalysts remains unexplored. In this
study, a series of Fe-based MOFs (denoted as MOF-R, where R = H, Cl,
or Br) with comparable structures are synthesized by changing the
organic linkers coordinated with the Fe metal active center, with
the aim of investigating the influence of halogen-containing linkers
on the OER activity. Significantly, MOF-Br exhibited superior OER
activity compared to MOF-Cl and MOF-H. Density functional theory calculations
reveal that the tuning of halogen groups on organic linkers can modulate
the electronic structure of the metal active sites and effectively
regulate the adsorption behavior of key intermediates near the optimal
d-band center, leading to the enhancement of electroactivity. Notably,
the bromine-substituted MOF-Br catalyst displayed remarkable intrinsic
OER activity, including a low overpotential of 251.2 mV at a current
density of 10 mA cm–2 and a low Tafel slope of 44.5
mV dec–1, surpassing the halogen-unsubstituted MOF-H
(262.6 mV and 63.4 mV dec–1) and commercial IrO2 (335.3 mV and 98.6 mV dec–1). Moreover,
the high turnover frequency at an overpotential of 300 mV was measured
to be 0.537 s–1, which is 30 times greater than
that of the commercial IrO2 catalyst (0.018 s–1). This research offers a potential strategy for designing MOF electrocatalysts
with superior OER activity, laying a solid foundation for the rational
design and synthesis of excellent OER electrocatalysts in the future.