Heterointerface engineering of NiFe (oxy)hydroxides/CNTs by in situ anchoring of sub-nano Au for efficient water oxidation

Heterointerface engineering of NiFe (oxy)hydroxides is a prospective way of improving OER activity by the pre-catalysis of metal hydroxides accompanying the modulation of defects, but enhancement of the kinetics is controversial. Herein, in situ phase transformation of NiFe hydroxides was proposed and heterointerface engineering was optimized by sub-nano Au anchoring in simultaneously formed cation vacancies. Controllable size and concentrations of anchored sub-nano Au in the cation vacancies resulted in the modulation of the electronic structure at the heterointerface, and improved water oxidation activity was ascribed to the enhanced intrinsic activity and charge transfer rate. Here, Au/NiFe (oxy)hydroxide/CNTs with an Fe/Au molar ratio of 24 exhibited an overpotential of ∼236.3 mV at 10 mA cm^-2 in 1.0 M KOH under simulated solar light irradiation, which is ∼19.8 mV lower than that without the consumption of solar energy. Spectroscopic studies reveal that the photo-responsive FeOOH in these hybrids and modulation of sub-nano Au anchoring in cation vacancies are favorable in improving solar energy conversion and suppressing photo-induced charge recombination.