A portable photoelectrochemical
(PEC) device is developed by intergating
a self-powered electrochromic tablet for visual analysis. The tablet
consists of an electron-injector (EI) part for photo-to-electric conversion
and an electrochromic (EC) part for visualized readout, which are
coated with dye-sensitized titanium dioxide film and Ni-doped tungsten
trioxide (WO<sub>3</sub>) film, respectively. Under the illumination
of a white LED light, the photoexcited electrons generated from EI
part convey to EC part through the conductive inner side of indium
tin oxide slide and would cause color change of the Ni-doped WO<sub>3</sub> film in the presence of protons. Furthermore, the Ni-doped
WO<sub>3</sub> film exhibits excellent transmittance modulation of
more than 80%, providing an enhanced signal for visual analysis. Using
pyrophosphate ion (PPi) as a model analyte, we have successfully constructed
a visualized PEC sensing platform based on the formation of blue-colored
hydrogen tungsten bronzes via the hydrolysis reaction of PPi. Being
equipped with a small light source and a dark box, the PEC tablet
as a portable device can perform colorimetric measurement with good
reversibility and stability. This smart PEC device provides important
reference for future studies on the visual application in practice
