Ni(OH)2-based materials are widely studied in oxygen
evolution reaction (OER), but no related synthesis, electrocatalytic
application, or theoretical analysis of Sn4+-doped Ni(OH)2 has been reported. In this work, Sn–Ni(OH)2 with a homogeneously distributed nanosheet array was synthesized
through a one-step hydrothermal process. It displays a hugely enhanced
catalytic activity compared to undoped Ni(OH)2 throughout
the OER and hydrogen evolution reaction (HER) processes. The overpotentials
at 100 mA cm–2 of Sn–Ni(OH)2 are
312 mV (OER) and 298 mV (HER), which are lower than the corresponding
396 and 427 mV of Ni(OH)2, respectively. In addition, Sn–Ni(OH)2 can deliver stable large current densities (at ≈500
and ≈1000 mA cm–2) for the long-term (>100
h) chronoamperometry testing. Moreover, Sn–Ni(OH)2 illustrates catalytic activity comparable to that of a commercial
Pt/C||RuO2 electrode pair during the overall water splitting
course. Both experimental phenomena and relevant computed theoretical
data confirm that the enhanced water splitting activity is mainly
due to the introduced Sn4+ site, which acts as the active
center activates the nearby Ni sites during the OER, while acting
as the most active reaction site that participates in the HER. Although
the doped Sn4+ has two different effects on OER and HER
proceedings, water splitting performance of Sn–Ni(OH)2 has been conspicuously improved.