To learn more about anion and cation effects, and the kinetics of the HOR/HER we turn our attention to the underpotential deposited hydrogen (H-upd) (Fig. ). Historically, the name originates from the charge observed at potentials more positive than the HER onset potential in argon and associated with the deposition of atomic hydrogen. A distinction was later introduced between H-upd, and hydrogen adsorbed on the platinum surface at negative potentials from the HER onset value (H-opd). We think that such a distinction is unnecessary, the H-upd already consisting of multiple contributions from hydrogen adsorbed on different sites and will use the term H-upd to describe all charge associated to hydrogen adsorption/desorption regardless of potential. Commonly, the H-upd charge is determined in argon at scan rates ≤ 50 mV/s. However, the H-upd features are maintained even at high scan rates, such as in Fig. . The advantage of employing high scan rates is that we can study the Hupd in the presence of H2, by separating its contribution from the steady state current, associated with the HOR/HER (Fig. ).