Electrochemistry targets the control of the conversion between electrical energy and chemical energy. It represents an exciting field in which long-standing environmental and energy-related issues can be addressed. A comprehensive theoretical understanding of electrochemical reactions and processes is essential for accelerating the development of materials for novel clean-energy-related devices, such as water electrolyzers, fuel cells, batteries, supercapacitors, and solar cells. To achieve this goal, numerical modeling methods have been developed to advance computational studies of the properties of electrocatalysts and the underlying elementary reaction mechanisms. The interests and efforts of scientists active in this hot topic motivate the publication of the collection of computational methods assembled in this book.