Electrocatalytic oxygen and hydrogen evolution reactions at Ni3B/Fe2O3 nanotube arrays under visible light radiation

Abstract

We demonstrate that arrays of Ni₃B/Fe₂O₃ nanotubes (NTAs) supported by a Fe foil can simultaneously boost the kinetics of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) after exposure to visible light radiation (OER and HER overpotentials decreased by 162 and 150 mV at 10 mA cm⁻², respectively). With a small band gap, Fe₂O₃ efficiently harnesses solar energy for the overall photoelectrochemical water splitting. Consequently, a current density of 10 mA cm⁻² requires only 1.50 V under one-sun illumination. Surface and spectroscopic analyses indicate that photoholes at the Fe₂O₃ NTAs transfer to Ni₃B, rendering the Ni₃B surface easier to oxidize into β-Ni(OH)₂, which is ultimately converted into the OER-catalyzing γ-NiOOH species at a relatively low anodic potential. Photoelectrons become localized at the HER-active Ni sites in Ni₃B. This work integrates photochemistry with electrocatalysis, affording a new avenue for developing high-performance and cost-effective photoelectrocatalysts for energy conversion applications.