The study investigates the effect of pH on the hydrogen oxidation and evolution reaction (HOR/HER) rates for three active monometallic surfaces: Pt, Ir, and Pd carbon-supported catalysts. Kinetic data were obtained using a proton exchange membrane fuel cell (PEMFC) and a rotating disk electrode (RDE) in 0.1 M NaOH. Key findings include: 1. A similar 100-fold decrease in activity for all surfaces when moving from low to high pH. 2. The reaction rate on Pt/C is controlled by the Volmer step. 3. The H-binding energy is the sole descriptor for HOR/HER in alkaline electrolytes. The study proposes a new mechanism for HOR/HER on Pt-metals in alkaline electrolytes, suggesting that the Volmer step is the rate-determining step and that H-UPD species are not necessary to describe HOR/HER rates. The results highlight the importance of understanding the microscopic reactions and the role of H-binding energy in designing advanced electrocatalysts for alkaline fuel cells and electrolyzers.The study investigates the effect of pH on the hydrogen oxidation and evolution reaction (HOR/HER) rates for three active monometallic surfaces: Pt, Ir, and Pd carbon-supported catalysts. Kinetic data were obtained using a proton exchange membrane fuel cell (PEMFC) and a rotating disk electrode (RDE) in 0.1 M NaOH. Key findings include: 1. A similar 100-fold decrease in activity for all surfaces when moving from low to high pH. 2. The reaction rate on Pt/C is controlled by the Volmer step. 3. The H-binding energy is the sole descriptor for HOR/HER in alkaline electrolytes. The study proposes a new mechanism for HOR/HER on Pt-metals in alkaline electrolytes, suggesting that the Volmer step is the rate-determining step and that H-UPD species are not necessary to describe HOR/HER rates. The results highlight the importance of understanding the microscopic reactions and the role of H-binding energy in designing advanced electrocatalysts for alkaline fuel cells and electrolyzers.