Combined Experimental-Numerical Analysis of Transient Phenomena in a Photoelectrochemical Water Splitting Cell

Abstract

A combined experimental-numerical approach was used to study transient phenomena occurring in a photoelectrochemical cell using a membrane-separated porous TiO 2 -based photoanode and a dark Pt-based cathode. The effects of three parameters (pH in the anodic compartment, operating cell temperature, and cathode compartment preconditioning with hydrogen) on the photocurrent was systematically investigated using design of experiments and analysis of variance. A theoretical model was developed able to accurately reproduce and predict the measurements. The model indicated that the electrochemical reaction uses two parallel pathways on the anodic interface. The first pathway represented the rapid charging of surface states and the subsequent formation of acidic titanol groups at the TiO 2 /H 2 O interface which, upon illumination, caused an anodic overshoot at a short time scale. These states recombined with the formed O 2 at a longer time scale which resulted in a current decrease after the overshoot. The second pathway was governed by transfer processes of H + ions at the TiO 2 /Nafion interface and caused the observed current increase under illumination and positive relaxation in the dark, both at long time scales. A negative undershoot was observed when the reverse electrolysis reaction was preferred.

Tin and Oxygen-Vacancy Co-doping into Hematite Photoanode for Improved Photoelectrochemical Performances

“…The obvious attenuation of transient photocurrent can be explained by the surface recommendation of the photogenerated carriers during the transfer process from photoelectrode surface into electrolyte [41]. Transfer efficiency that shows the decay and overshoot characteristic of surface electronhole recombination is calculated as the ratio of J transient and J steady [42,43]. Here, we define J transient as the very beginning photocurrent when the light irradiation is introduced, and J steady as the steady photocurrent before turning off the light irradiation.…”

Harvesting Hydrogen Gas from Air Pollutants with an Unbiased Gas Phase Photoelectrochemical Cell

“…[16] This proofof-concept is thus an important step in the development of stand-alone PEC cells for simultaneousp ollutanta batement and energy recuperation, but still offers ample room for improvement in follow-up studies. This effect is much more pronouncedi nt he presence of methanol.…”

“…This is av ery encouraging result that spurs further investigation of PEC-based air treatment for energy recovery.I na ddition, it should be stressed that all these resultsa re obtained without applying external bias and the electrode materials are www.chemsuschem.org not yet fully optimized toward cell performance. [16] This proofof-concept is thus an important step in the development of stand-alone PEC cells for simultaneousp ollutanta batement and energy recuperation, but still offers ample room for improvement in follow-up studies. For instance, ongoing investigationsb yo ur group involvem odification of the anode material with plasmonic alloy nanoparticles, of which we showed they can span the entire UV/Vis spectrum therebye ffectively increasing solar photon utilization.…”

“…(16)] it is clear that in the aerobic pathway both photogenerated electrons and H + ions are consumed. Notably,f rom [Eq.…”

“…Notably,f rom [Eq. (16)] it is clear that in the aerobic pathway both photogenerated electrons and H + ions are consumed. This will consequently lower the available photocurrent, which corresponds to what we observe experimentally( Figure 2).…”