p-Type Transparent Conducting Oxide/n-Type Semiconductor Heterojunctions for Efficient and Stable Solar Water Oxidation

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• 作者：Le Chen ; Jinhui Yang ; Shannon Klaus ; Lyman J. Lee ; Rachel Woods-Robinson ; Jie Ma ; Yanwei Lum ; Jason K. Cooper ; Francesca M. Toma ; Lin-Wang Wang ; Ian D. Sharp ; Alexis T. Bell ; Joel W. Ager
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：August 5, 2015
• 年：2015
• 卷：137
• 期：30
• 页码：9595-9603
• 全文大小：633K
• ISSN：1520-5126

文摘

Achieving stable operation of photoanodes used as components of solar water splitting devices is critical to realizing the promise of this renewable energy technology. It is shown that p-type transparent conducting oxides (p-TCOs) can function both as a selective hole contact and corrosion protection layer for photoanodes used in light-driven water oxidation. Using NiCo₂O₄ as the p-TCO and n-type Si as a prototypical light absorber, a rectifying heterojunction capable of light driven water oxidation was created. By placing the charge separating junction in the Si using a np⁺ structure and by incorporating a highly active heterogeneous Ni鈥揊e oxygen evolution catalyst, efficient light-driven water oxidation can be achieved. In this structure, oxygen evolution under AM1.5G illumination occurs at 0.95 V vs RHE, and the current density at the reversible potential for water oxidation (1.23 V vs RHE) is >25 mA cm^鈥?. Stable operation was confirmed by observing a constant current density over 72 h and by sensitive measurements of corrosion products in the electrolyte. In situ Raman spectroscopy was employed to investigate structural transformation of NiCo₂O₄ during electrochemical oxidation. The interface between the light absorber and p-TCO is crucial to produce selective hole conduction to the surface under illumination. For example, annealing to produce more crystalline NiCo₂O₄ produces only small changes in its hole conductivity, while a thicker SiO_x layer is formed at the n-Si/p-NiCo₂O₄ interface, greatly reducing the PEC performance. The generality of the p-TCO protection approach is demonstrated by multihour, stable, water oxidation with n-InP/p-NiCo₂O₄ heterojunction photoanodes.