Presenter(s): Adrian Gordon − Chemistry
Faculty Mentor(s): Shannon Boettcher
Poster 38
Research Area: Natural/Physical Science
Funding: Vice President for Research and Innovation (VPRI) Undergraduate Fellowship
Photoelectrochemical cells, which split water into hydrogen, a clean fuel, and oxygen, have shown great potential for efficiently storing solar energy. In these cells, the oxygen evolution half reaction (OER) limits the efficiency of the entire solar water splitting process. Therefore, accurate OER efficiency measurements are critical in evaluating electrode catalyst materials. Currently efficiency is measured using solution species known as hole scavengers. These species are assumed to collect all photogenerated holes, and thus indicate the energy conversion efficiency of the system. However, this assumption does not hold true for an entire class of OER catalysts, including two promising catalysts, nickel and iron, because of their “conductivity switching” behavior. Hole scavengers introduce energetic losses in these electrodes.
To quantify these energetic losses, in situ electrical measurements were taken to isolate electronic properties of the catalyst from those of the semiconductor on model photoanodes. Dual Working Electrode technique was used to collect data on two model systems: silicon and hematite coated with impermeable and permeable catalysts, respectively. It was found that hole scavengers hold surface catalysts, such as Ni, in their reduced state, thus creating an extraction barrier for holes generated in the semiconductor, and lowering the efficiency of electrochemical cells.