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Impact of Electrocatalyst Activity and Ion Permeability on Water-Splitting Photoanodes
journal contribution
posted on 2015-12-17, 08:34 authored by Fuding Lin, Benjamin F. Bachman, Shannon W. BoettcherElectrocatalyst
(EC)-modified semiconductor (SC) photoelectrodes
are key elements of solar water-splitting systems. The SC|EC interface
affects the composite photoelectrode behavior but is poorly understood.
We uncover the role of EC activity and SC|EC interface properties
using a range of metal (Ni, Fe, Ni–Fe, Co, Ir) oxide or (oxy)hydroxide
ECs deposited on model single-crystal n-TiO2 photoanodes. The impedance and photoelectrochemical response of
the system was nearly independent of EC oxygen evolution activity
if the catalyst was deposited electrochemically as an ion-permeable
(oxy)hydroxide or hydrous oxide. When dense oxides (e.g., ion-impermeable)
ECs were used, the response depended strongly on the EC. These data
demonstrate that the EC and SC interface structures are more important
than the EC activity in determining the composite photoanode response,
confirming recent SC|EC interface simulations for ion-permeable ECs.
These results thus inform the design of high-performance water-oxidizing
photoanodes with direct SC|EC interfaces.