Enhancement of Z-scheme Water Splitting Activity on Printable Photocatalyst Sheets by Controlling Electronic Properties of a Transparent Conductive Colloid

Hiromasa Tokudome^a^,^b, Sayuri Okunaka^a^,^b, Shingo Oozu^a^,^b, Takeshi Ikeda^a^,^b, Kazunari Domen^c^,^d

^aResearch Institute, TOTO LTD.

^bJapan Technological Research Association of Artifical Photosynthetic Chemical Process (ARPChem)

^cUniversity of Tokyo, Japan, Japan

^dCenter for Energy & Environmental Science, Shinshu University

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting19 (NFM19)

#SolFuel19. Solar Fuel Synthesis: From Bio-inspired Catalysis to Devices

Berlin, Germany, 2019 November 3rd - 8th

Organizers: Roel van de Krol and Erwin Reisner

Poster, Hiromasa Tokudome, 389
Publication date: 18th July 2019

Photocatalytic water splitting is attracted much attention as a new production process for renewable hydrogen utilizing abundant sunlight. This reaction is known to mainly proceed in two excitation ways, single step and two step excitation (“Z-scheme”). In particular, it has been an increasing concern about Z-scheme overall water splitting to which can be applied various visible light responsive photocatalysts that can reduce or oxidize water. As a practical approach for solar hydrogen production using Z-scheme mechanism, we developed a film device called as a printable photocatalyst sheet. This sheet possesses a simple structure consisted of mixed films of two kinds of visible-light-active photocatalysts (for example, Rh-doped SrTiO3 and BiVO4 for hydrogen and oxygen evolution) and a conductive mediator nanocolloid on a glass substrate. Moreover, the sheet can be satisfied both of cost-effectiveness and large scalability due to the easy fabrication by screen printing. The sheet incorporating a colloidal Au mediator exhibited a fairly good solar-to-hydrogen energy conversion efficiency (STH) of 0.1% [1]. Recently, we designed a new photocatayst sheet based on transparent colloidal mediator to improve the photoabsorption of the sheet in visible region. An indium-tin-oxide (ITO) was applied as a transparent mediator, attaining the STH ~ 0.4% [2].

In this study, we propose a printable photocatalyst sheet based on a new transparent mediator, antimony (Sb) -doped tin oxide (ATO), which is widely used as a low-cost anti-electrostatic agent. Although the ATO colloid has lower electro-conductivity than the above-mentioned ITO one, the ATO-incorporated sheet showed the similar water-splitting activity to the ITO-added one under visible light. The activity was further improved by changing the Sb concentration, and the best sample showed about twice greater activity than the ITO-based sheet.

References:

[1] Wang, Q.; Hisatomi, T.; Jia, Q.; Tokudome, H.; Zhong, M.; Wang, C.; Pan, Z.; Takata, T.; Nakabayashi, M.; Shibata, N.; Li, Y.; Sharp, I-D.; Kudo, A.; Yamada, T.; Domen, K. Scalable water splitting on particulate photocatalyst sheets with a solar-to-hydrogen energy conversion efficiency exceeding 1%. Nat. Mater., 2016, 15, 611–615.

[2] Wang, Q.; Okunaka, S.; Tokudome, H.; Hisatomi, T.; Nakabayashi, M.; Shibata, N.; Yamada, T.; Domen, K. Printable Photocatalyst Sheets Incorporating a Transparent Conductive Mediator for Z-Scheme Water Splitting. Joule 2018, 2, 2667-2680.

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