Humidity-voltaic characteristics of Au–porous silicon interfaces

The humidity-voltaic effect, i.e. generation of open-circuit voltage (Voc), in Au–porous silicon (PS) interface in humid atmosphere (up to 450 mV at 95% relative humidity) in dark and daylight illumination is discovered. The humidity-stimulated voltage generation is attributed to the splitting of water and hydrogen molecules on the surfaces of the Au catalyst, where further diffusion penetration of hydrogen ions into the Au–PS interface results in the formation of dipoles, thus inducing Voc across dipoles. The generation of Voc (up to 550 mV) has also been observed on dipping of Au–PS structures in different hydrogen-containing solutions (ethanol, benzine, sodium tetraborate pentahydrate, etc). Data of response time-dependent changes of the open-circuit voltage generated in Au–PS structures under humid conditions were used for the estimation of diffusion coefficients of hydrogen. The temperature dependence of the diffusion coefficient of hydrogen at 323–353 K via the pore surfaces of PS is attributed to be D = 1.3 × 10−2exp (−0.25/kT).