Combined effect of nano-structured NiCo2S4 coated hematite photoanodes for efficient photoelectrochemical water oxidation

Abstract

• Thiospinel NiCo 2 S 4 electrocatalyst coated on 1-D hematite nanorods for low bias PEC water oxidation. • The intrinsic effects of NiCo 2 S 4 on PEC water oxidation is discussed in detail. • NiCo 2 S 4 facilitated to reveal the intrinsic photovoltage of hematite, and hastened the water oxidation kinetics. A major challenge in photo electrochemical (PEC) water oxidation is the generation of hydrogen at a low external bias. Herein, thiospinel NiCo 2 S 4 particles were grown on Sn-doped hematite 1D nanorods for low bias PEC water oxidation via a simple hydrothermal method. Upon incorporation of NiCo 2 S 4 over hematite, the photocurrent increased from 0.85 to 1.51 mA cm –2 with a cathodic/negative shift in the onset potential of ∼330 mV. In addition, the intrinsic photovoltage of hematite increased from 180 to 290 mV upon illumination. These collective improvements originated from the inherent electrocatalytic activity of NiCo 2 S 4 in the water oxidation reaction. The core level electrochemical analyses confirmed that the inclusion of NiCo 2 S 4 hastened the charge injection at the electrode/electrolyte interface by suppressing the charge accumulation and recombination, eventually reducing the kinetic over potential.