Photoelectrochemical Water Splitting with Thin Film Semiconductors

Lead by Prof. David Tilley

We investigate “emerging” semiconductor-based materials for photoelectrochemical water splitting, with a focus on those materials comprised of Earth-abundant elements and fabricated using simple and scalable methods. Thus far we have targeted copper-based materials, due to the abundance of copper and facile preparation methods for copper oxides and copper sulfides. We recently reported a favorable heterojunction partner (CdS) for emerging material CuO (Figure 1) that enabled record photovoltages to be obtained.

Figure 1: Cross-sectional SEM image of a cupric oxide-based photocathode for photoelectrochemical hydrogen evolution. The CdS acts as an electron extraction layer while the TiO2 protects the underlying materials from corrosion in the aqueous environment. (Chemistry of Materials, 2017)

The materials are characterized under simulated AM 1.5 G solar irradiation (100 mW/cm2). The current density–voltage characteristics are shown in Figure 2, where the onset of hydrogen producing photocurrents occurs at approximately +0.45 V/RHE and 1.68 mA/cm2 of photocurrent are produced at 0V/RHE. This level of photocurrent would correspond to ~2% solar-to-hydrogen (STH) efficiency in a tandem cell where the electrical bias is provided by an additional photovoltaic junction.

figure current density
Figure 2: Current density-voltage curve of a CuO/CdS heterojunction photocathode in pH 7 phosphate buffer under chopped simulated AM 1.5 G solar radiation (100 mW/cm2). (Chemistry of Materials, 2017)