Electrocatalytic Oxygen and Hydrogen Evolutions at Ni3B/Fe2O3 Nanotube Arrays under Visible Light Radiation
We demonstrate that arrays of Ni3B/Fe2O3 nanotubes (NTAs) supported by a Fe foil can simultaneously boost the kinetics of 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/cm2, respectively). With a small band gap, Fe2O3 efficiently harness solar energy for the overall photoelectrochemical water splitting. Consequently, a current density of 10 mA/cm2 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 to β-Ni(OH)2, which is ultimately converted to 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.