Hydrogen is considered as a promising clean energy carrier for the future. Since Fujishima and Honda originally reported that a TiO2 based photoelectrochemical cell could be used to split water into hydrogen and oxygen in 1972,[1] intensive researches have been done to improve the performance of the photoelectrochemical water splitting cell in the past forty years. However, the solar energy conversion efficiency is still low, it is necessary to explore some materials with high conversion efficiency.

A p-n photoelectrochemical cell is a highly desirable approach to realize high conversion efficiency[2]. The photocurrent in a p-n photoelectrochemical cell is determined by the photoelectrode with the lower photocurrent. To date, several p-type semiconductor photocathodes with high solar photocurrent (dozens of mA cm-2) have been developed.[3-4] Some promising visible-light-responsive photoanode materials have also been studied by us and other researchers. Though different methods have been used to improve performance of a photoanode, all of these photoanodes exhibit much lower solar photocurrent (lower than 4 mA cm-2)[5-6] than the photocathodes, which is a bottleneck for water splitting in a p-n photoelectrochemical cell. Therefore, finding an efficient photoanode is a key step in solar water splitting for hydrogen production.

In this study, we prepared the Ta3N5 photoelectrodes by modified thermal oxidation and nitridation method.[7] A high solar photocurrent @1.23 VRHE of 5.5 mA cm-2 was obtianed on the Ta3N5 photoanode by facile thermal or mechanical exfoliation of the surface recombination centers. This strategy can offer guidance to improve photoelectrochemical performance of other materials.

References:

[1] Fujishima, A. ; Honda, K. Nature 1972, 238, 37-38.

[2] Walter, M. G. ; Warren, E. L. ; McKone, J. R. ; Boettcher, S. W. ; Mi, Q. ; Santori, E. A. ; Lewis, N. S. Chem. Rev. 2010, 110, 6446-6473.

[3] Boettcher, S. W.; Warren, E. L. ; Putnam, M. C. ; Santori, E. A.; Tuner-Evans, D.; Kelzenberg, M. D. ; Walter, M. G.; McKone, J. R.; Brunschwig, B. S. ; Atwater, H. A.; Lewis, N. S. J. Am. Chem. Soc. 2011, 133, 1216-1219.

[4] Lee, M. H.; Takei, K.; Zhang, J.; Kapadia, R. ; Zheng, M.; Chen, Y.; Nah, J.; Matthews, T. S. , Chueh, Y.; Ager, J. W. ; Javey, A. Angew. Chem. Int. Ed. 2012, 51, 10760-10764.

[5] Luo, W.; Yang, Z. ; Li, Z. ; Zhang, J. ; Liu, J.; Zhao, Z. ; Wang, Z.; Yan, S.; Yu, T.; Zou, Z. Energy Environ. Sci. 2011, 4, 4046-4051.

[6] Li, Y. ; Takata, T. ; Cha, D.; Takanabe, K. ; Minegishi, T.; Kubota, J.; Domen, K. Adv. Mater. 2013, 25, 125-131.

[7] Li, M. ; Luo, W. ; Cao, D. ; Zhao, X. ; Li, Z. ; Yu, T.; Zou, Z. Angew. Chem. Int. Ed. 2013, 52, 11016-11020

Wenjun Luo

Nanjing University

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