Advanced Operando /In Situ Spectroscopy Studies on Photocatalysis for Solar Water Splitting

By utilizing high-energy electrons/holes excited by sunlight to drive water splitting, photocatalysis has become a promising route to produce clean hydrogen fuel. Conversion of light to chemical energy in solar water splitting is a sequential kinetic process involved in light absorption, charge separation, charge migration to surface of photocatalyst particles, and surface chemical reactions on active sites. Because this sequential process spans about 15 orders of magnitude from femtosecond to second, time-resolved and operando / in situ techniques are desired to understand detailed evolution processes. Owing to the flexible and tunable characteristics of electromagnetic wave, spectroscopic techniques have become effective strategies to achieve time-resolved and operando / in situ studies on photocatalysis for solar water splitting. Here, this chapter focuses on various operando / in situ spectroscopy techniques throughout the entire electromagnetic spectrum to understand the catalytic elementary process in solar water splitting. Depending on the specifically spectroscopic response, these techniques propel our understanding and knowledge of water splitting/conversion/forming in photocatalysis and electrocatalysis from the view of time domain, space domain, energetics, structure level, and reaction intermediates.