Figure 17.1  Electric vehicles and smartphones are powered by batteries, devices that harness the energy of spontaneous redox reactions.

Batteries power the devices all around us from our smartphones and laptops to electric vehicles and more! The source of this power is a type of chemical reaction called an oxidation-reduction reaction – more commonly referred to as a redox reaction.

In the first section of this chapter, we introduce the chemistry of redox reactions. This important reaction class is defined by changes in oxidation states for one or more reactant elements, and it includes a subset of reactions involving the transfer of electrons between reactant species. Around the turn of the nineteenth century, chemists began exploring ways these electrons could be transferred indirectly via an external circuit rather than directly via intimate contact of redox reactants. In the two centuries since, the field of electrochemistry has evolved to yield significant insights on the fundamental aspects of redox chemistry as well as a wealth of technologies ranging from industrial-scale metallurgical processes to robust to rechargeable batteries for modern technologies (Figure 17.1). In this chapter, the essential concepts of electrochemistry will be addressed.