期刊
ACS APPLIED MATERIALS & INTERFACES
卷 13, 期 14, 页码 16317-16325出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c00826
关键词
photoelectrochemical water splitting; photoelectrodes; electrocatalysts; surface modification; Ta3N5; oxygen evolution reaction
资金
- Artificial Photosynthesis Project from the New Energy and Industrial Technology Development Organization
- JSPS [19K15670]
- Grants-in-Aid for Scientific Research [19K15670] Funding Source: KAKEN
The transparent Ta3N5 photoanode is a promising candidate for the front-side photoelectrode in a tandem cell, focusing on semiconductor properties and interfacial design. While stable photoanodic response was observed for Ta3N5/SiO2 in the nonaqueous phase, the addition of water led to immediate deactivation.
A transparent Ta3N5 photoanode is a promising candidate for the front-side photoelectrode in a photoelectrochemical (PEC) cell with tandem configuration (tandem cell), which can potentially provide high solar-to-hydrogen (STH) energy conversion efficiency. This study focuses in particular on the semiconductor properties and interfacial design of transparent Ta3N5 photoanodes fabricated on insulating quartz substrates (Ta3N5/SiO2), typically the geometric area of 1 x 1 cm(2) in contact with indium on its edge. This material utilizes the self-conductivity of Ta3N5 to make the PEC system operational, and the electrode would strongly reflect the intrinsic nature of Ta3N5 without a back contact that is commonly introduced. First, PEC measurements using acetonitrile (ACN)/H2O mixed solution were made to elucidate the intrinsic photoresponse in the presence of tris(2,2'-bipyridine)ruthenium(II) bis(hexafluorophosphate) (Ru-(bpy)(3)(PF6)(2)) without water contact which avoids a multielectron-transfer oxygen evolution reaction (OER) and photoinduced self-oxidation. The potential difference between the onset potential of Ru2+ PEC oxidation by Ta3N5/SiO2 and the redox potential of Ru2+/3+ in the nonaqueous environment was about 0.7 V. While a stable photoanodic response was observed for Ta3N5/SiO2 in the nonaqueous phase, the addition of a small quantity of water into this nonaqueous system led to the immediate deactivation of Ta3N5/SiO2 photoanode under illumination by self-photooxidation to form TaOx at the solid/water interface. In aqueous phase, flatband potentials estimated from Mott-Schottky analysis varied with solution pH (constant potential against reversible hydrogen electrode (RHE)). Photoelectrode modification by a transparent NiFeOx layer was attempted. The complete coverage of the Ta3N5 surface with transparent NiFeOx electrocatalysts, achieved by an optimized spin-coating protocol with controlled Ni-Fe precursors, allowed for the successful protection of Ta3N5 and demonstrated an extremely stable photocurrent for hours without any additional protective layers. The stability of the resultant NiFeOx/Ta3N5/SiO2 was limited not by Ta3N5 but mainly by a NiFeOx electrocatalyst due to Fe dissolution with time.
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