read this https://www.nature.com/articles/srep13801

Hi Gohain,

Tafel slope is an important parameter to predict the type of HER mechanism i.e whether the HER process will proceed by Volmer Heyrovsky or Volmer Tafel mechanism. For instance, if the value of Tafel slope is in the range of 30 to 40, it means the HER follows Vomer-Tafel mechanism. Tafel step and Heyrovsky step both are related to desorption of hydrogen molecule from electrocatalyst surface. So, depending on the properties of your electrocatalyst, desorption of H2 will occur either by Heyrovsky step or Tafel step. The role of Tafel slope is to predict this mechanism.