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Understanding Surface Recombination Processes Using Intensity‐Modulated Photovoltage Spectroscopy on Hematite Photoanodes for Solar Water Splitting
Author(s) -
Liu Yongpeng,
Guijarro Néstor,
Sivula Kevin
Publication year - 2020
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.202000064
Subject(s) - overlayer , photocurrent , water splitting , chemistry , hematite , passivation , optoelectronics , surface photovoltage , oxide , renewable energy , spectroscopy , materials science , photocatalysis , catalysis , physics , mineralogy , biochemistry , organic chemistry , layer (electronics) , quantum mechanics , electrical engineering , engineering
Converting solar energy into hydrogen through photoelectrochemical (PEC) water splitting offers a promising route towards a fully renewable energy economy. A fundamental understanding of photogenerated charge recombination processes in semiconducting photoelectrodes is a key consideration in optimizing solar water splitting cells and intensity‐modulated photovoltage spectroscopy (IMVS) has recently emerged as a promising technique for gaining new insight. However, the interpretation of IMVS data under various conditions (that is, when photoelectrodes are in sacrificial electrolytes or employ catalytic overlayers) is not complete. Using IMVS data we present herein an analysis of charge recombination processes under open circuit conditions on a model photoanode system: nanostructured hematite. Employing two sacrificial oxidation conditions compared to standard water oxidation conditions, our IMVS results establish a direct correlation between surface recombination processes and the low frequency IMVS response. We found that surface intermediate states for water oxidation under open circuit condition exhibit a lifetime of 229 ms under standard illumination conditions. Applying a nickel iron oxide overlayer also gives insight into surface passivation effects through IMVS analysis of photoanode system.