Open AccessPlanar and Nanostructured n‐Si/Metal‐Oxide/WO 3 /BiVO 4 Monolithic Tandem Devices for Unassisted Solar Water Splitting
Author(s) -
Ahmet Ibbi Y.,
Berglund Sean,
Chemseddine Abdelkrim,
Bogdanoff Peter,
Präg Raphael F.,
Abdi Fatwa F.,
van de Krol Roel
Publication year - 2020
Publication title -
advanced energy and sustainability research
Language(s) - English
Resource type - Journals
ISSN - 2699-9412
DOI - 10.1002/aesr.202000037
Subject(s) - materials science , heterojunction , chemical vapor deposition , photocurrent , nanorod , water splitting , nanotechnology , chemical engineering , photocatalysis , optoelectronics , catalysis , chemistry , biochemistry , engineering
A series of planar and nanostructured core‐shell photoanodes composed of n‐Si/SiO x /TiO 2 /WO 3 /BiVO 4 heterojunctions are fabricated by chemical deposition methods. Aerosol‐assisted chemical vapor deposition (AA‐CVD) is utilized for the large area production of planar SnO 2 and TiO 2 thin films and compact WO 3 nanorods, with the subsequent formation of WO 3 /BiVO 4 core‐shell nanostructures via solution deposition. Optimized monolithic dual photoanodes consisting of n‐Si/SiO x /TiO 2 /WO 3 /BiVO 4 /Fe(Ni)OOH and a Pt cathode as the hydrogen evolution catalyst, provide a combined photo‐voltage capable of unassisted solar water splitting with a maximum photocurrent density of 0.3 mA cm −2 in 1.0 m KB i pH 9.3 buffer solution under solar simulated AM 1.5 G illumination. An average faradaic efficiency of ≈98% is confirmed by operando differential electrochemical mass spectroscopy (DEMS) for H 2 production. Solid‐state J–V measurements of the individual n‐Si/SiO x /MO (MO = WO 3 , BiVO 4 , TiO 2 , or SnO 2 ) interfaces in the dark and under illumination provide valuable insights into the unfavorable electrical properties at n‐Si/SiO x /WO 3 or n‐Si/SiO x /BiVO 4 junctions. The insertion of metal oxide buffer layers, such as SnO 2 and TiO 2 , can mitigate surface recombination at the junctions between n‐Si/SiO x and WO 3 or BiVO 4 and strongly enhances the overall photovoltage.