Journal
SOLAR ENERGY
Volume 191, Issue -, Pages 151-160Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.solener.2019.08.070
Keywords
ZnO; Surface modification; H2O2; Hole scavenger; Cathodic current; Visible light water splitting
Categories
Funding
- National Research Foundation of Korea (NRF) - Korea government (MSIT) [2019R1A2C1008746]
- Basic Science Research Program through the National Research Foundation of Korea (NRF) - Ministry of Education [2016R1D1A1B03932515]
- National Research Foundation of Korea [2019R1A2C1008746, 2016R1D1A1B03932515] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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In the present work, we explored the hole scavenging activity of hydrogen peroxide (H2O2) on flake-like Co-doped ZnO thin films to improve the visible light photoelectrochemical (PEC) water splitting activity. To address this phenomenon, we developed promising Co (0, 0.8, 1.7 and 2.2 at.%)-doped ZnO thin films by simultaneous RF and DC magnetron sputtering. First, precise control on Co doping level in the ZnO host lattice has been demonstrated to facilitate superior water splitting activity through the strategic surface transformation. Accordingly, Co doping concentration significantly modulated the structural properties of ZnO (0 0 2). From FESEM analysis, clear morphological changes were observed from granular (Co-0 at.%) to flake-like (Co-1.7 at.%). Also, AFM analysis provided insights into surface roughness (7.0 nm) and maximum height of roughness (35 nm) of Co (1.7 at.%)-ZnO thin films. Furthermore, TEM analysis highlighted the crystalline changes on Co (1.7 at.%)-ZnO thin films. Thus, Co (1.7 at.%)-ZnO exhibited a reduced band gap (3.07 eV). Notably, flake-like Co (1.7 at.%)-ZnO thin films validated with prominent hydrophilicity. As a result, the morphology of Co (1.7 at.%)-ZnO facilitated superior visible light PEC activity than others. Second, to accelerate the PEC activity, hole scavenging mechanism has been proposed by the addition of H2O2 into the KOH. Our results show how the HO2* radicals contributed to suppressing the hole accumulation, recombination and cathodic currents at the interface of Co-ZnO/electrolyte. Overall, we believe that the proposed hole scavenger strategy provides new insight into improved visible light PEC water splitting activity on flake-like Co-ZnO thin films.
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