This handbook focuses on electrocatalytic materials, a field that has experienced significant advancements in recent decades, primarily driven by nanoscale catalyst design improvements. These advancements have been crucial in the development and enhancement of alternative energy technologies relying on electrochemical reactions. Electrocatalytic materials play a vital role in reducing over-potentials required for electrochemical device operation. As a prominent subset of catalysts, they facilitate essential reactions for energy conversion and storage through electron transfer processes. However, studying electrocatalytic materials presents challenges due to complex reaction networks, diverse selectivity possibilities, and intricate reaction mechanisms. This book offers an extensive description of electrocatalysis and the materials used in electrocatalytic processes. It covers cutting-edge studies and in-depth discussions on the applications of electrocatalytic materials in energy conversion and storage (including fuel cells, water splitting, batteries, etc.), sensors, and other potential applications. It also addresses the broader implications of electrocatalysis in academia and industry. Each section of the book highlights the latest developments, contemporary challenges, and state-of-the-art investigations aimed at producing valuable outcomes for end users. With contributions from diverse experts, this comprehensive resource is essential for researchers, scientists, industrialists, educators, and students.