Abstract
Photoelectrochemical water splitting is considered as a long-term solution for the ever-increasing energy demands. Various strategies have been employed to improve the traditional TiO2 photoanode. In this study, TiO2 nanorods were decorated by graphitic carbon nitride (C3N4) derived from different precursors such as thiourea, melamine, and a mixture of thiourea and melamine. Photoelectrochemical activity of TiO2/C3N4 photoanode can be modified by tuning the number of precursors used to synthesize C3N4. C3N4 derived from the mixture of melamine and thiourea in TiO2/C3N4 photoanode showed photocurrent density as high as 2.74 mA/cm2 at 1.23 V vs. RHE. C3N4 synthesized by thiourea showed particle-like morphology, while melamine and melamine with thiourea derived C3N4 yielded two dimensional (2D) nanosheets. Nanosheet-like C3N4 showed higher photoelectrochemical performance than that of particle-like nanostructures as specific surface area, and the redox ability of nanosheets are believed to be superior to particle-like nanostructures. TiO2/C3N4 displayed excellent photostability up to 20 h under continuous illumination. Thiourea plays an important role in enhancing the photoelectrochemical performance of TiO2/C3N4. This study emphasizes the fact that the improved photoelectrochemical performance can be achieved by varying the precursors of C3N4 in TiO2/C3N4 heterojunction. This is the first report to show the influence of C3N4 precursors on photoelectrochemical performance in TiO2/C3N4 systems. This would pave the way to explore different precursors influence on C3N4 with respect to the photoelectrochemical response of TiO2/C3N4 heterojunction photoanode.
Highlights
Photoelectrochemical water splitting is one of the ideal methods for solar energy conversion.Enormous efforts have been made to achieve remarkable solar to hydrogen efficiency since the discovery of TiO2 photoelectrochemical performance
We have demonstrated the impact of the three different precursors of C3 N4 such as thiourea, melamine, and mixture of thiourea and melamine with the ratio of 1:1.5 on photoelectrochemical performance of TiO2 /C3 N4 heterojunction
The photocurrent density of 2.74 mA/cm2 at 1.23 V vs. RHE was achieved g-C3N4/TiO2 nanorod for TiO2 /C3 N4 photoanode, which is the highest photocurrent density compared to previous reports, C3N4/TiO2 nanotube to the best of our knowledge
Summary
Photoelectrochemical water splitting is one of the ideal methods for solar energy conversion. C3 N4 can be synthesized by simple thermal polymerization of abundantly available nitrogen rich precursors such as thiourea, melamine, urea, and dicyanamide Application of this material into photoelectrochemical water splitting only started recently, even though C3 N4 has desirable band gap and oxidation and reduction potentials [6]. Semiconductors with staggered band alignments can be coupled to fabricate the heterojunction, which can improve the solar water oxidation of the photoelectrode due to the increased charge carrier separation [7,8,9,10,11]. We have demonstrated the impact of the three different precursors of C3 N4 such as thiourea, melamine, and mixture of thiourea and melamine with the ratio of 1:1.5 on photoelectrochemical performance of TiO2 /C3 N4 heterojunction. This work provides a promising approach to improve solar water oxidation performance of TiO2 /C3 N4 heterojunction
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