High-Resolution Analysis of Photoanodes for Water Splitting by Means of Scanning Photoelectrochemical Microscopy

In pursuance of efficient tools for the local analysis and characterization of novel photoelectrocatalytic materials, several SECM-based techniques have been developed, aiming on the combined benefit of a local irradiation of the analyzed sample and a microelectrode probe for the localized electrochemical analysis of the surface. We present the development and application of scanning photoelectrochemical microscopy (SPECM) for the laterally resolved characterization of photoelectrocatalytic materials. Particularly, the system was developed for the photoelectrochemical characterization of n-type semiconductor-based photoanodes for water splitting. By using the tip microelectrode simultaneously for local irradiation and as an electrochemical probe, SPECM was capable to simultaneously provide information about the local photocurrent generated at the sample under irradiation and to detect the photoelectrocatalytically evolved oxygen at the microelectrode. In combination with a novel means of irradiation of the interrogated sample, local analysis of semiconductor materials for light-induced water splitting with improved lateral resolution is achieved

Fe–Cr–Al Containing Oxide Semiconductors as Potential Solar Water-Splitting Materials

A high-throughput thin film materials library for Fe–Cr–Al-O was obtained by reactive magnetron cosputtering and analyzed with automated EDX and XRD to elucidate compositional and structural properties. An automated optical scanning droplet cell was then used to perform photoelectrochemical measurements of 289 compositions on the library, including electrochemical stability, potentiodynamic photocurrents and photocurrent spectroscopy. The photocurrent onset and open circuit potentials of two semiconductor compositions (n-type semiconducting: Fe₅₁Cr₄₇Al₂Ox, p-type semiconducting Fe_36.5Cr_55.5Al₈O_<i>x</i>) are favorable for water splitting. Cathodic photocurrents are observed at 1.0 V vs RHE for the p-type material exhibiting an open circuit potential of 0.85 V vs RHE. The n-type material shows an onset of photocurrents at 0.75 V and an open circuit potential of 0.6 V. The p-type material showed a bandgap of 1.55 eV, while the n-type material showed a bandgap of 1.97 eV