Role of WO3 Layers Electrodeposited on SnO2 Inverse Opal Skeletons in Photoelectrochemical Water Splitting

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• 作者：Gun Yun ; Maheswari Balamurugan ; Hyun-Sik Kim ; Kwang-Soon Ahn ; Soon Hyung Kang
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：March 24, 2016
• 年：2016
• 卷：120
• 期：11
• 页码：5906-5915
• 全文大小：672K
• ISSN：1932-7455

文摘

Tin dioxide (SnO<sub>2sub>) inverse opals (IOs) were developed by a spin-coating-assisted sol–gel process. The SnO<sub>2sub> IOs exhibited a pore size of ∼260 nm in the 370 nm sized polystyrene bead (PS) templates. Electrodes having a WO<sub>3sub> layer with a band gap (E<sub>gsub>) of 2.6 eV were electrodeposited on the SnO<sub>2sub> IOs under a constant potential (−0.47 V<sub>Ag/AgClsub>), where the thickness of the WO<sub>3sub> layer depended on the applied charge amount for WO<sub>3sub> electrodeposition (200–800 mC/cm<sup>2sup>). As a control sample, a pure WO<sub>3sub> IO film with the same thickness of ∼3.1 μm was also prepared by electrodeposition. The pore diameter of the SnO<sub>2sub> IO structure declined noticeably as the deposited charge amount of the WO<sub>3sub> layer increased from 200 to 800 mC/cm<sup>2sup>, leading to eventual coverage of the SnO<sub>2sub> IO structure with the WO<sub>3sub> (800 mC/cm<sup>2sup>) layer. Moreover, X-ray diffraction analysis indicated a steady increase of the signal intensity of the monoclinic WO<sub>3sub> planes as the deposited charge amount of the WO<sub>3sub> layer increased, indirectly indicating an increased loading amount of the WO<sub>3sub> layer. However, the optimum photoelectrochemical (PEC) response was achieved with the SnO<sub>2sub>/WO<sub>3sub> (600 mC/cm<sup>2sup>) IO electrode, which exhibited the highest photocurrent density (J<sub>scsub>) of 2.8 mA/cm<sup>2sup> under full-sun conditions and 0.91 mA/cm<sup>2sup> under visible light, indicating that the enhancement of the J<sub>scsub> under visible light contributed significantly to the improvement of the total J<sub>scsub>, compared with the values for the pure SnO<sub>2sub>, SnO<sub>2sub>/WO<sub>3sub> (200, 400, and 800 mC/cm<sup>2sup>), and WO<sub>3sub> IO electrodes. Furthermore, the favorable cascading band alignment between the SnO<sub>2sub> and WO<sub>3sub> layers promoted rapid charge separation and charge transport through the conductive SnO<sub>2sub> IO skeleton. Therefore, the heterojunction, formed from the highly conductive SnO<sub>2sub> core layer and visible-light-absorbing WO<sub>3sub> shell layer, can boost the PEC activity by complementary combination of the unique advantages of the materials.