Correlating hydrogen oxidation and evolution activity on platinum at different pH with measured hydrogen binding energy

Abstract

The hydrogen oxidation/evolution reactions are two of the most fundamental reactions in distributed renewable electrochemical energy conversion and storage systems. The identification of the reaction descriptor is therefore of critical importance for the rational catalyst design and development. Here we report the correlation between hydrogen oxidation/evolution activity and experimentally measured hydrogen binding energy for polycrystalline platinum examined in several buffer solutions in a wide range of electrolyte pH from 0 to 13. The hydrogen oxidation/evolution activity obtained using the rotating disk electrode method is found to decrease with the pH, while the hydrogen binding energy, obtained from cyclic voltammograms, linearly increases with the pH. Correlating the hydrogen oxidation/evolution activity to the hydrogen binding energy renders a monotonic decreasing hydrogen oxidation/evolution activity with the hydrogen binding energy, strongly supporting the hypothesis that hydrogen binding energy is the sole reaction descriptor for the hydrogen oxidation/evolution activity on monometallic platinum.

Towards Versatile and Sustainable Hydrogen Production through Electrocatalytic Water Splitting: Electrolyte Engineering

“…In the study, the M−H binding energy in various conditions was also determined by cyclic voltammograms. The investigation of the HER performance (the potential at −1 mA cm −2 ), in conjunction with the M−H binding energy strength, indicated that both the HER performance and M−H binding energy shift monotonically with the solution pH 80. Such an observation is in agreement with the conventional view of the reaction (the activity–binding energy relation: the Sabatier principle).…”

“…However, the study focused on a low current density region (ca. 1 mA cm −2 ),80 which is much smaller than the target for solar fuel production (8.2 mA cm −2 or 10 mA cm −2 ). Thus, as a next step, studies of the HER in more practical conditions are necessary.…”

“…Accordingly, most studies dedicated to the HER have been conducted in highly acidic73, 74, 75, 76, 77, 78, 79, 80 and 0.1–1.0 mol L −1 alkaline78, 79, 80, 81, 82, 83 electrolyte solutions. This section aims to present the general aspects of the HER under the extreme pH conditions, based on which the significance of the ionic effects will be introduced.…”

“…There have been a couple of studies reported regarding the HER at near‐neutral pH in buffered solutions that function to maintain the local pH level 80, 119, 120. Experimentally, it was clearly demonstrated that the use of a buffered solution as a “supporting electrolyte” successfully prevented the diffusion limitation of hydronium ions at near‐neutral pH levels.…”

“…Experimentally, it was clearly demonstrated that the use of a buffered solution as a “supporting electrolyte” successfully prevented the diffusion limitation of hydronium ions at near‐neutral pH levels. Figure 7 shows the polarization curves obtained by using Pt in various electrolytes (including acetate, phosphate, and carbonate buffer) on the RHE scale 80…”