posted on 2016-05-09, 00:00authored byLeanne
G. Bloor, Renata Solarska, Krzysztof Bienkowski, Pawel J. Kulesza, Jan Augustynski, Mark D. Symes, Leroy Cronin
Solar-to-hydrogen photoelectrochemical
cells (PECs) have been proposed
as a means of converting sunlight into H2 fuel. However,
in traditional PECs, the oxygen evolution reaction and the hydrogen
evolution reaction are coupled, and so the rate of both of these is
limited by the photocurrents that can be generated from the solar
flux. This in turn leads to slow rates of gas evolution that favor
crossover of H2 into the O2 stream and vice
versa, even through ostensibly impermeable membranes such as Nafion.
Herein, we show that the use of the electron-coupled-proton buffer
(ECPB) H3PMo12O40 allows solar-driven
O2 evolution from water to proceed at rates of over 1 mA
cm–2 on WO3 photoanodes without the need
for any additional electrochemical bias. No H2 is produced
in the PEC, and instead H3PMo12O40 is reduced to H5PMo12O40. If the
reduced ECPB is subjected to a separate electrochemical reoxidation,
then H2 is produced with full overall Faradaic efficiency.