  Photocatalytic- and Photoelectrochemical water splitting is currently
performed using radiation sources with wavelengths < 1000 nm, i.e. in the near
infrared range (NIR). The fact that water has a broad absorption band, which
lies at wavenumbers between 3000 and 3700 cm-1 (stretching mode) and 1650 cm-1
(bending mode), has not been taken into account so far. We irradiated the steel
anode with a mid-infrared LED (lambda=3300 nm) while water electrolysis was
performed in pH 7-corrected phosphate buffer solution. A significant shift (270
mV) of the cyclic voltammetry (CV) curve towards lower potential values was
obtained when the radiation source was on. To the best of our knowledge, this
is the first report describing the use of a mid-infrared radiation source to
increase the efficiency of water electrolysis.
