A conformal coating strategy with nanocarbon to enhance photoelectrochemical responses and the long-term stability of ZnO quantum dots is described. Strong anchoring bonds between a ZnO core and nanocarbon shell ameliorate the poor electrochemical stability of ZnO (such as photocorrosion) in liquid electrolyte. The conjugation of the graphene QD and C60 to the ZnO QDs leads to 71% and 99% quenching of the UV photoluminescence (PL) emission, respectively. Also, the decay time of the nanocomposites at UV wavelengths measured much faster than that for the reference of bare ZnO QDs. The moderate energy states and good charge conductance of the nanocarbons result in ultrafast charge transport from the ZnO core to the nanocarbon shell. Thereby, the ZnO core-nanocarbon shell quantum dots shows significantly improved light harvesting performance. The PEC cell test for water oxidation and conventional degradation test using organic dyes exhibited that the photoelectrochemical activities could be significantly improved. At 1.23V (vs. RHE) in pH 6.9 electrolyte, 6 times enhanced photocurrent density was achieved by the conformal coating with C60 (0.235mA/cm2 for ZnO-C60 photoanodes). In particular, the strong Zn-O-C bond structures on the ZnO surface prevented photoinduced holes from being consumed by the photocorrosion reaction of ZnO, thereby improving long-term stability.
Bibliographical noteFunding Information:
J. K. Kim and J. H. Park acknowledges the support by the NRF of Korea Grant funded by the Ministry of Science, ICT and Future Planning (NRF- 2013R1A2A1A09014038 , 2009-0083540 ) and the Global Ph. D Fellowship Program through the NRF (grant number 2012H1A2A1016034 ). S. Bae and D. I. Son appreciate the financial support from the KIST Institution Program, the R&D Convergence Program of MSIP (Ministry of Science, ICT and Future Planning) and ISTK (Korea Research Council for Industrial Science and Technology) of Republic of Korea (GrantCAP-13-2-ETRI). This research was supported by Global Frontier Program through the Global Frontier Hybrid Interface Materials (GFHIM) of the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT & Future Planning ( 2013M3A6B1078867 ).
Jung Kyu Kim is currently a Ph.D. candidate under the supervision of Prof. Jong Hyeok Park at SKKU Advanced Institute of Nano-technology (SAINT) and school of chemical engineering in Sungkyunkwan University, Korea. He is also a researcher in the institute of science and technology at Sungkyunkwan University. He has been granted the Global Ph.D. Fellowship program by NRF of Korea since 2012. His research focuses on the efficient heterojunction light harvesting devices with tailored nanostructures; including the organic based or the organic–inorganic hybrid based heterojunction solar cells, and solar-to-hydrogen conversion devices.
© 2015 Elsevier Ltd.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)
- Electrical and Electronic Engineering