Ni3S2-Decorated TiO2 nanotube arrays as effective photoanodes for photoelectrochemical water splitting

Abstract

Cocatalyst nickel sulfide (Ni₃S₂) was successfully loaded onto TiO₂ nanotube array (TiO₂ NTA) photoanodes for the first time by a simple two step hydrothermal process. The prepared Ni₃S₂/TiO₂ NTA photoanode shows better photoelectrochemical (PEC) water splitting activity compared to pure TiO₂ NTAs. The surface photovoltage (SPV) spectroscopy and transient photocurrent measurements provide direct evidence for the efficient charge separation of the Ni₃S₂/TiO₂ NTA photoanode. Furthermore, the work function measurement proved the formation of the interfacial electric field at the interface of Ni₃S₂ and TiO₂, which is the main driving force of charge separation. Photoelectrochemical impedance spectroscopy (PEIS) measurements and oxygen evolution reaction (OER) polarization curves confirmed that the Ni₃S₂/TiO₂ NTA photoanode effectively reduces the interfacial charge transfer resistance and suppresses the overpotential of water oxidation, which make the photogenerated holes take part in the water oxidation reaction easily. These results demonstrate that Ni₃S₂ could be an excellent cocatalyst when applied in PEC water oxidation.