Hydrogen has been widely used in industrial processes. However, most of the hydrogen produced today comes in the form of grey hydrogen, which is obtained from the cracking of hydrocarbons. An alternative method for generating hydrogen is through water electrolysis, which produces both hydrogen and oxygen. However, the efficiency of hydrogen production is limited by the availability of effective electrocatalysts for the hydrogen evolution reaction (HER). In this chapter, we provide a comprehensive list of electrocatalysts used for HER and discuss how their intrinsic properties can be modified through various strategies. These modifications can tune the electronic structure, such as the d-band center, and ultimately influence their activity in hydrogen production.