CHAPTER 6: Rapid Screening Methods in the Discovery and Investigation of New Photocatalyst Compositions

Discovery of an efficient, stable, and inexpensive photocatalyst is a key issue in the design of a practical photoelectrochemical (PEC) system for converting solar energy into chemical fuels, e.g. hydrogen production from water splitting. Despite over 40 years of enormous efforts in the area, no photocatalyst has yet been found as an optimized material for water photolysis. In this chapter, combinatorial rapid synthesis and screening of semiconducting materials to discover and improve photocatalysts for water photolysis are discussed. While several different techniques are briefly touched upon, the focus is on using modified scanning electrochemical microscopy (SECM) for combinatorial rapid screening. In this application of SECM, a piezo-dispensing tip and a fiber optic are placed in the SECM for rapid synthesis and fast scanning of the semiconductor spot arrays. The rapid synthesis and screening of electrocatalysts decorating the semiconducting photocatalysts, which is required to further enhance the water splitting reactions, i.e. hydrogen/oxygen evolution reactions (HER/OER), is also explained. In addition, several modes of SECM used to study material properties and chemical reactions on photocatalysts/electrocatalysts are generally introduced. Finally, factors affecting the activity of photocatalysts are briefly discussed to guide the rapid screening of materials in PEC systems.