The electrochemical hydrogen evolution reaction (HER) is growing in significance as society begins to rely more on renewable energy sources such as wind and solar power. Thus, research on designing new, inexpensive, and abundant HER catalysts is important. Here, we describe how a simple experiment combined with results from density functional theory (DFT) can be used to introduce the Sabatier principle and its importance when designing new catalysts for the HER. We also describe the difference between reactivity and catalytic activity of solid surfaces and explain how DFT is used to predict new catalysts based on this. Suited for upper-level high school and first-year university students, this exercise involves using a basic two-cell electrochemical setup to test multiple electrode materials as catalysts at one applied potential, and then constructing a volcano curve with the resulting currents. The curve visually shows students that the best HER catalysts are characterized by an optimal hydrogen binding energy (reactivity), as stated by the Sabatier principle. In addition, students may use this volcano curve to predict the activity of an untested catalyst solely from the catalyst reactivity. This exercise circumvents the complexity of traditional experiments while it still demonstrates the trends of the HER volcano known from literature. (Contains 1 table and 4 figures.)