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 (SnO₂) inverse opals (IOs) were developed by a spin-coating-assisted sol–gel process. The SnO₂ IOs exhibited a pore size of ∼260 nm in the 370 nm sized polystyrene bead (PS) templates. Electrodes having a WO₃ layer with a band gap (E_g) of 2.6 eV were electrodeposited on the SnO₂ IOs under a constant potential (−0.47 V_Ag/AgCl), where the thickness of the WO₃ layer depended on the applied charge amount for WO₃ electrodeposition (200–800 mC/cm²). As a control sample, a pure WO₃ IO film with the same thickness of ∼3.1 μm was also prepared by electrodeposition. The pore diameter of the SnO₂ IO structure declined noticeably as the deposited charge amount of the WO₃ layer increased from 200 to 800 mC/cm², leading to eventual coverage of the SnO₂ IO structure with the WO₃ (800 mC/cm²) layer. Moreover, X-ray diffraction analysis indicated a steady increase of the signal intensity of the monoclinic WO₃ planes as the deposited charge amount of the WO₃ layer increased, indirectly indicating an increased loading amount of the WO₃ layer. However, the optimum photoelectrochemical (PEC) response was achieved with the SnO₂/WO₃ (600 mC/cm²) IO electrode, which exhibited the highest photocurrent density (J_sc) of 2.8 mA/cm² under full-sun conditions and 0.91 mA/cm² under visible light, indicating that the enhancement of the J_sc under visible light contributed significantly to the improvement of the total J_sc, compared with the values for the pure SnO₂, SnO₂/WO₃ (200, 400, and 800 mC/cm²), and WO₃ IO electrodes. Furthermore, the favorable cascading band alignment between the SnO₂ and WO₃ layers promoted rapid charge separation and charge transport through the conductive SnO₂ IO skeleton. Therefore, the heterojunction, formed from the highly conductive SnO₂ core layer and visible-light-absorbing WO₃ shell layer, can boost the PEC activity by complementary combination of the unique advantages of the materials.