3 / 31
Page 75
Notes:
Innovative Energy & Research | ISSN: 2576-1463 | Volume 7
Renewable Energy and Resources
Energy Materials and Fuel Cell Research
2
nd
International Conference on
&
August 27-28, 2018 | Boston, USA
Photoelectrochemical materials for sunlight-driven water splitting devices
Hiroshi Nishiyama
The University of Tokyo, Japan
P
hotocatalysis or photoelectrochemistry are attractive developing fields of engineering for building free-running sunlight-
driven water splitting to generate H
2
and O
2
. We are surveying solar-spectrum-responding semiconductive materials
as the candidates for the visible light absorbers in the H
2
+O
2
harvesting devices. We have been fabricating and testing
water photo-splitting devices composed of a pair of photocathode (p-type, for H
2
) and photoanode (n-type, for O
2
) both
decorated with catalysts for evolving those gases. As for photocathode, we developed H
2
evolving flat layered sheets based on
chalcopyrite Cu(In, Ga)Se
2
(CIGS, the cutoff wavelength of absorption ~ 1100 nm) and its doped versions with Zn, S, etc. The
photocurrent obtained by the solar simulator (AM 1.5G) can afford more than 10% of solar hydrogen conversion efficiency.
The photoanode material is the remaining problem to solve. BiVO
4
(~540 nm), paired with CIGS, realized a stable operation
for the stoichiometric faradaic evolution of H
2
and O
2
, however, the maximum solar-to-H
2
efficiency has been below 4 %.
Obviously, we need n-type light absorbers with longer cutoff wavelength. We are also developing transition metal nitrides and
oxynitrides for the sunlight absorbers. Ta
3
N
5
(~600 nm) has been the most intensively investigated, as particles embedded
on metal layers (particle transferred sheets) and flat layered thin films, both of which can serve as photoanodes. Foreign
materials can be assembled as the background layer or capping layer for the Ta
3
N
5
layer to improve the electronic properties
and robustness as an electrode immersed in the electrolytic solution. We will discuss the best performance for Ta
3
N
5
and
oxynitrides as O
2
-evolving photoelectrodes energized by solar irradiation.
Biography
Hiroshi Nishiyama completed his Ph.D. at Nagaoka University of Technology, Japan in 2005. In 1998–2013, he was an assistant professor at the Analysis and
Instrumentation Center at Nagaoka University of Technology. He is currently a principal project researcher in the R&D Laboratory of Artificial Photosynthetic Chem-
ical Process (ARPChem) at The University of Tokyo. His research focuses on the development of high-performance photoanode electrodes and high-performance
PEC systems.
nishiyama@arpchem.t.u-tokyo.ac.jpHiroshi Nishiyama, Innov Ener Res 2018, Volume 7
DOI: 10.4172/2576-1463-C2-006