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Inverted Pyramid Textured p‑Silicon Covered with Co2P as an Efficient and Stable Solar Hydrogen Evolution Photocathode

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posted on 24.06.2019, 00:00 by Sitaramanjaneva Mouli Thalluri, Bin Wei, Katharina Welter, Rajesh Thomas, Vladimir Smirnov, Liang Qiao, Zhongchang Wang, Friedhelm Finger, Lifeng Liu
Silicon (Si) has been investigated as a promising photoelectrode material for use in photoelectrochemical water splitting. However, development of Si photocathodes that can operate at a high photocurrent density for solar-driven hydrogen production with long-term stability remains challenging. Herein, we report the fabrication of inverted pyramid textured p-Si photocathodes covered conformally and continuously with a thickness-gradient cobalt phosphide (Co2P) layer, which not only effectively isolates p-Si from aqueous electrolyte to avoid corrosion but also efficiently catalyzes the solar-driven hydrogen evolution reaction (HER). Thanks to the unique inverted pyramid structure, the drop-cast Co2P can distribute all over the p-Si photocathode and form a macroscopically continuous but locally nonuniform layer on the sidewalls of each inverted pyramid. The local nonuniform distribution enables light absorption to be partially separated from catalytic activity. Consequently, the as-fabricated Co2P-coated p-Si photocathode exhibits a high photocurrent density of 35.2 mA cm–2 at 0 V versus the reversible hydrogen electrode under AM 1.5G illumination and can photoelectrochemically catalyze the HER above 30 mA cm–2 at least 150 h without notable degradation.