Interfacing catalysts to photovoltaics is an attractive approach to artificial photosynthesis.[1] However, the realization of silicon based solar-to-fuel devices is challenging due to the intrinsic instability of this material under aqueous conditions, particularly at high pH. A widely studied approach to enhance stability is to employ protective surface coatings, such as TiO2 or transparent conducting oxides.[2,3] However, these coatings frequently result in interfacial charge transfer efficiency losses. Here, we report that direct deposition of catalysts onto nanotextured pn junction Si devices enables effective protection of Si from photocorrosion at high pH (pH = 14), even in the absence of an additional interfacial corrosion protection layer. Nanotexturing of Si was achieved via physical sputtering under an applied substrate bias, which was verified using atomic force microscopy (AFM). Subsequent deposition of Ir or CoOx as the catalyst yielded photoelectrochemical water oxidation below the reversible thermodynamic potential Figure 1. <img src='https://acs-archive-assets2.s3.amazonaws.com/240nm/uploads/45478_figure.jpg' alt='' />. In contrast to the planar pn junction Si devices, which quickly failed, those on nanotextured substrates maintained stable activity . X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES), as well as contact potential difference and surface photovoltage measurements, are utilized to determine the composition and interfacial energy alignments.This work highlights a general approach that may be used to improve the stability of photoelectrodes by engineering the catalyst/semiconductor interfaces.

Stable light-induced water oxidation at catalyst/silicon electrodes with nanotextured interfaces

247th National Meeting (2014)

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