Designing Co-Pi Modified One-Dimensional n–p TiO2/ZnCo2O4 Nanoheterostructure Photoanode with Reduced Electron–Hole Pair Recombination and Excellent Photoconversion Efficiency (&gt;3%)

5 years ago

Designing Co-Pi Modified One-Dimensional n–p TiO2/ZnCo2O4 Nanoheterostructure Photoanode with Reduced Electron–Hole Pair Recombination and Excellent Photoconversion Efficiency (>3%)

Gobinda Gopal Khan, Ayan Sarkar, Keshab Karmakar

The poor visible light absorption, defect-mediated charge carrier recombination, slow water oxidation kinetics, and charge transportation limit the performance of TiO₂ photoelectrodes for water oxidation. In order to tackle these issues, here a one-dimensional photoanode is designed by electrodepositing a p-ZnCo₂O₄ nanolayer on n-TiO₂ nanotubes surface and finally electrochemically coupling the TiO₂/ZnCo₂O₄ surface with an ultrathin layer of the cobalt phosphate (Co-Pi) catalyst nanoparticles. These typical TiO₂/ZnCo₂O₄@Co-Pi nanoheterostructures exhibit a remarkably enhanced visible light driven photoelectrochemical property with applied bias photoconversion efficiency (ABPE) ∼ 3% at 0.2 V vs NHE. The TiO₂/ZnCo₂O₄@Co-Pi nanoheterostructures also show enhanced visible light absorption with large photocurrent density ∼440% higher than that of the TiO₂ nanotubes electrode at 1.2 V vs Ag/AgCl and significantly low onset potential for water oxidation. Studies on the transient photocurrent and flat-band potential demonstrate the remarkable improvement in the photogenerated charge carrier separation or reduced recombination because of the favorable band alignment at the heterointerface. The Co-Pi catalyst further boosts the water oxidation reaction by reducing electron–hole pair recombination through the suppression of the surface trap states. Moreover, Co-Pi also serves as a hole-acceptor layer, improving the charge-transfer kinetics for an enhanced photoelectrochemical performance.

Publisher URL: http://dx.doi.org/10.1021/acs.jpcc.7b08213

DOI: 10.1021/acs.jpcc.7b08213