Boosting catalytic activity with a p–n junction: Ni/TiO2 nanotube arrays composite catalyst for methanol oxidation

Abstract

Ni nanoparticles were loaded on TiO2 nanotube arrays (Ni/TiO2NTs) via pulsed electrodeposition method and employed as catalyst for methanol oxidation in alkaline media. The as-prepared Ni/TiO2NTs catalyst was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical analyzer. The electrochemical studies showed that Ni/TiO2NTs under illumination exhibited higher catalytic activity and stronger poisoning-tolerance for methanol oxidation than that in the dark. The effect of illumination which improved catalytic activity of Ni/TiO2NTs were attributed to the p–n junction formed at the interface between Ni(OH)2 and TiO2NTs resulting in the photo-generated holes flow into Ni(OH)2, thus, the transmitted holes boosted the oxidation of Ni(OH)2 and produced the OH to oxidize methanol and intermediates that absorbed on the catalyst. The present study shows Ni/TiO2NTs can act as a promising candidate for the anode catalyst in photo assist direct methanol fuel cells (PDMFCs) application.