Structural and Photoelectrochemical Properties of p-Cu_2O Nano-Surfaces Prepared by Oxidizing Copper Sheets with a Slow Heating Rate Exhibiting the Highest Photocurrent and H_2 Evaluation Rate

U. S. Liyanaarachchi ； C. A. N. Fernando ； K. L. Foo ； U. Hashim ； M. Maza

《Chinese Journal of Physics》 53卷2期 (2015/04) Pp. 143-160

https://doi.org/10.6122/CJP.20141222B

並列摘要

Well cleaned commercially available copper sheets were heated maintaining different temperature profile heating rates for fabricating p-Cu_2O nano-surfaces. Initially a heating rate of 10℃ min^(-1) was provided inside the furnace with copper sheets starting from room temperature until the temperature reached, respectively, 300℃, 400℃, 450℃, and 700℃, then the temperature was kept constant for 30 min, and then cooled down to room temperature. A single phase nano-p-Cu_2O was found for the 300℃, 400℃, and 450℃ temperature profiles, this may be due to maintaining a slow heating rate avoiding the formation of CuO. Samples prepared from 700℃ temperature profile contained both the p-Cu_2O and CuO phases. Different surface morphology changes were observed from the AFM micrographs for the samples prepared with the different temperature profiles. A photo-current enhancement was found for the photoelectrochemical cell (PEC) with p-Cu_2O nano-surfaces produced from the 450℃ temperature profile in comparison to that of the samples prepared from the other temperature profiles. Material characterization from XRD, AFM, FTIR spectra, diffuse reflectance spectra, VI characteristics, time development of the photo-current, Mott- Schottky plots, and estimated band positions were presented for discussing the mechanism of the photo-current enhancement and the highest H2 generation for the 450℃ temperature profile produced p-Cu_2O PEC. The highest photocurrent (≈ 10 mAcm^(-2)) and H2 evolution rate (≈ 130×10^(-4) Moles l^(-1)min^(-1)) was observed in the presence of a 1 M Na_2SO_4 electrolyte buffered at a pH of 4.9 with a biased voltage-0.4 V vs Ag/AgCl for the nano-surfaces produced from the 450℃ temperature profile, with comparison to the recently reported highest H_2 evolution rate and highest photocurrent studied by Gratzel and co-workers [A. Parachino, V. Laporte, K. Sivula, M. Gratzel, and E. Thimsen, Nature. Mat. 10, 456 (2011)] providing the same experimental conditions that they have maintained in their experimental work.