Three-dimensionally patterned Ag-Pt alloy catalyst on planar Si photocathodes for photoelectrochemical H-2 evolution

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Platinum is still the most active element for the hydrogen evolution reaction (HER); however, it suffers from its scarcity and high cost. Thus, significant efforts have been dedicated to maximize the catalytic activity with less loading. When Pt is utilized at a semiconductor surface, more factors have to be considered. Placing a catalyst directly in contact with a semiconductor supports the extraction of photogenerated minority carriers as well as boosts the catalytic reactions. In addition, a catalyst should be designed with prudence not to interfere in the light path with respect to absorption at the underlying substrate. Herein, we report the development of planar Si-based photocathodes, covered with a native oxide, for the HER, which also satisfy the prerequisites for the use of a three-dimensionally patterned, flower-like Ag-Pt catalyst. The catalyst consisted of nanoparticles of homogeneously alloyed Ag and Pt, fabricated by a galvanic exchange of Pt with Ag. Importantly, these two elements were proven to have their own functionalities. Ag not only contributed to transporting e(-) and H-ad to the Pt for subsequent processes of the HER but also effectively extracted minority carriers by diluting the high work function of Pt, leading to a better Schottky barrier at the catalyst-insulator-semiconductor junction. Furthermore, computational simulation revealed that the proposed catalyst pattern alleviated optical light loss with the increasing catalyst loading compared to the two-dimensional case. Owing to these effects, we could achieve 0.36 V (vs. reversible hydrogen electrode) as an open circuit potential and the near maximum current density of planar p-type Si. The findings in this work suggests deeper insights that could support the design of catalysts for solar-fuel systems.
Publisher
ROYAL SOC CHEMISTRY
Issue Date
2019-01
Language
English
Article Type
Article
Citation

PHYSICAL CHEMISTRY CHEMICAL PHYSICS, v.21, no.8, pp.4184 - 4192

ISSN
1463-9076
DOI
10.1039/c8cp07304j
URI
http://hdl.handle.net/10203/254135
Appears in Collection
EE-Journal Papers(저널논문)
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