Enhanced photoelectrochemical performance of hydrothermally grown tetravalent impurity (Si4+) doped zinc oxide nanostructures for solar water splitting applications
We report the photoelectrochemical performance of Si-doped ZnO nanorods (NRs) synthesized via two step sol–gel and hydrothermal technique. In the X-ray diffraction patterns the prominent (002) peak confirms the hexagonal wurtzite phase for all samples. In addition to this, the Field Emission Scanning Electron Microscopy images also confirm the hexagonal shape of the NRs with the inclusion of this group IV dopant. The absorption spectra clearly indicates the increase in absorbance in the visible region after doping Si as compared with the undoped ZnO NRs. Bandgap tuning has been noted to be possible after doping. With the insertion of Si4+ ion into the ZnO matrix, the oxygen defects acting as recombination centers are reduced, as observed from the photoluminescence (PL) spectrum. We obtain a photocurrent density of 1.101 mA cm−2 values (approximately 4.5 times higher than the ZnO sample) at + 0.438 V in presence of 0.1 M NaOH electrolyte solution under visible light illumination (AM 1.5G) for the 8% Si-doped ZnO NRs sample. We attribute this enhancement to the reduction in recombination centers causing suppression of electron–hole recombination due to the reduced oxygen defects as observed in the PL spectrum. The enhanced absorption along with higher surface area of the NRs also promoted the increase in photocurrent value for this Si doped sample. The stability tests conceived that the doped ZnO NRs samples can better behave as a promising photoelectrode material for further generation of clean green energy.
The authors acknowledge the Department of Science and Technology (DST) for the project with Grant Number SR/FTP/PS-184/2012, SERB vide Dy. No. SERB/F/5439/2013-14 dated 25.11.2013 and Faculty Research Scheme-FRS (54)/2103-2014/APH. The authors would also like to thank the Ministry of Human Resource and Development project under the Scheme-Establishment of Centre of Excellence for Training and Research in Frontier Areas of Science and Technology (FAST) in Renewable Energy vide letter F. No. 5-5/2014-TS.VII dated 04.09.2014. The authors would like to thank Indian Institute of Technology (Indian School of Mines), Dhanbad, India for providing research fellowship and Central Research Facility (CRF) respectively. We are also thankful to Dr. K. Asokan, Scientist F, Materials Science Division, Inter University Accelerator Centre, New Delhi for his support in carrying out the Hall measurements. One of the authors M.C. would like to acknowledge Indo-US Science and Technology Forum (IUSSTF) for providing international Bhaskara Advanced Solar Energy (BASE-2016) fellowship.
- 27.H. Yuan, J. Mater. Sci. 23, 2075 (2012)Google Scholar
- 31.Y. Yang, S. Niu, D. Han, T. Liu, G. Wang, Y. Li, Adv. Energy Mater. 7, 1 (2017)Google Scholar
- 41.W. Körner, C. Elsässer, Phys. Rev. B 83, 1 (2011)Google Scholar