Electrochemistry can turn a favorable redox reaction, such as a vigorous reaction between reductive fuels and oxidant, into a process that outputs high-efficiency work. On the other hand, with the electrochemical driving force, it can also realize a non-favorable redox reaction, such as electrolysis of water or carbon dioxide to combustible fuels. Thus, electrochemical energy conversion offers a promising solution to cope with the challenges in energy and environmental applications. The key to realize such energy conversion processes is a high-performance electrocatalyst. The efficiency and performance are governed by the redox reactions that happen at the interface between the catalyst and the reactants. Spectroscopy is the perfect tool to unveil the nature of these critical chemical processes.  It can reveal the surface features/chemistry/structures that are favorable/unfavorable for the key redox reactions. On the basis of the obtained knowledge from spectroscopic studies, design strategies can be obtained and will serve as guiding principles to develop new materials chemistry and structures with optimized performance.