Storing solar energy in chemical form (e.g. hydrogen from water splitting), represents a promising route to enable a carbon-neutral society. Photoelectrochemical (PEC) water splitting holds the key to perform this process with simplicity and at high theoretical conversion efficiency. However, the realization of PEC H2 production at a global scale is limited by the current performance of semiconductor materials suitable for PEC. To advance the field, an improved fundamental understanding of the semiconductor-liquid junction (SCLJ), wherein the photoelectrosynthetic reaction is occurring, is urgently needed to identify the parameters limiting the performance and direct actions for their improvement. Here, we show how a toolbox of operando and in situ characterization techniques, namely, intensity-modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS), transient photocurrent/photovoltage spectroscopy (TPC/TPV), photoelectrochemical impedance spectroscopy (PEIS), in situ UV-Vis spectroscopy, and operando Raman spectroscopy can be used to gain deep insight of the competing processes at the SCLJ. We highlight our recent studies with emerging semiconducting photoelectrodes (CuIn0.3Ga0.7S2, ZnFe2O4, CuFe2O4, LaFeO3, CuFeO2), which have provided insights into the interfacial carrier behavior, i.e., energetic across the interface, kinetics of charge transfer and recombination, nature of the surface states, and chemical identity of intermediate species. In particular, we implement light modulation techniques (IMPS/IMVS) on CuFe2O4 to reveal an unfavourable kinetic competition which significantly hampers the charge transfer efficiency. Likewise, by fitting the impedance response with equivalent circuits, a clear map of the density of surface states is shown. Overall, these findings provide a better understanding on the electrochemical phenomena at the SCLJ, establishing a precise roadmap to engineer the interface and optimize the performance of solar fuel devices.

In situ and operando spectroelectrochemical techniques for evaluating interfacial carrier behavior in emerging photoelectrodes for solar fuel production

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.