Manipulating
the electronic structure of a catalyst at the atomic
level is an effective but challenging way to improve the catalytic
performance. Here, by stretching the Fe–O bond in FeOOH with
an inserted Mo atom, a Fe–O–Mo unit can be created,
which will induce the formation of high-valent Fe4+ during
the alkaline oxygen evolution reaction (OER). The highly active Fe4+ state has been clearly revealed by in situ X-ray absorption
spectroscopy, which can both enhance the oxidation capability and
lead to an efficient and stable adsorbate evolution mechanism (AEM)
pathway for the OER. As a result, the obtained Fe–Mo–Ni3S2 catalyst exhibits both superior OER activity
and outstanding stability, which can achieve an industrial-level current
density of 1 A cm–2 at a low overpotential of 259
mV (at 60 °C) and can stably work at the large current for more
than 2000 h. Moreover, by coupling with commercial Pt/C, the Fe–Mo–Ni3S2∥Pt/C system can be used in the anion
exchange membrane cell to acquire 1 A cm–2 for overall
water splitting at 1.68 V (2.03 V for 4 A cm–2),
outperforming the benchmark RuO2∥Pt/C system. The
efficient, low-cost, and ultrastable OER catalyst enabled by manipulating
the atomic structure may provide potential opportunities for future
practical water splitting.