In this talk, we address one of the most important challenges in photoanode research, namely the low photovoltage generated by large band gap semiconductors.  The prototypical material we chose to work on was hematite (a-Fe2O3) because it is a material with great promise in solar splitting water.  A critically important issue that prevents the promise from being realized is the small photovotlage generated by hematite (typically 2.0 eV).  By modifying the surface using a recently identified oxygen evolution catalyst (NiFeOx), we measured a photovoltage of 0.61 V.  A record-low turn-on voltage of 0.62 V (vs. reversible hydrogen electrode) was observed.  When combined with silicon nanowire dual absorbers, the turn-on potential was further reduced to 0.32 V.  These data represent the new benchmark for the hematite-based solar water splitting reactions.  Most significantly, we understand the working mechanism as a result of greater photovoltage generation but not kinetic overpotential reduction.  We present evidence that supports this radical idea.

Increasing photovoltage generation by hematite in photoelectrochemical water splitting reactions

247th National Meeting (2014)

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