Low-Cost Nanomaterials for Photoelectrochemical Water Splitting - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 263

Fig. 1 Principle of operation
of photoelectrochemical
water splitting cells based on
n type semiconductors.
Reproduced with permission
from [ 23 ]

converted to the potential versus RHE for calculating the solar conversion effi-
ciency. The conversion equation is expressed as followed [ 36 ]:

E RHE ¼ E Ag = AgCl þ 0 : 059 pH + E Ag = AgCl

where E RHE is the potential against RHE; E Ag/AgCl is the applied potential versus
Ag/AgCl reference electrode, pH is the pH value of the electrolyte solution and
E Ag = AgCl is the potential of reference electrode (Ag/AgCl) versus RHE electrode.
Platinum (Pt) structures (e.g., wire, plate, mesh) are typically used as counter
electrode, because Pt has the lowest overpotential for hydrogen evolution. The
most common parameter to evaluate the PEC performance of photoelectrodes is
the photocurrent density obtained under standard one sun illumination (AM 1.5G,
100 mW/cm 2 . However, the photocurrent density can vary based on the power and
the model of solar simulator and filters used for the experiment. Alternatively, the
electrode performance can also be evaluated by incident photon to current con-
version efficiency (IPCE). IPCE measurement presents the photoactivity of the
electrode as a function of monochromatic incident light wavelength. It can be
calculated with the following equation:

IPCE ¼ ð 1240 eV nm Þð I lA/cm 2 Þ
ð k nm Þð J lW/cm 2 Þ

100 %

where I is the photocurrent density obtained under the illumination of the
monochromatic light, k is the wavelength of the monochromatic light, J is the
power density of the monochromatic light. The equation shows that the IPCE