Figure 6.

Voltage breakdown of water electrolysis in buffered solutions at neutral pH. a) Voltage breakdown for the water electrolysis at a scan in K‐phosphate of 0.1 mol kg⁻¹ 80 °C, and b) in K‐phosphate of 4.1 mol kg⁻¹ 100 °C determined by electrocatalytic testing for the half‐cell reactions. η_i indicates the overpotential for process i. All measurements were performed in the three‐electrode configuration using IrO_x/Ti mesh, Pt/Pt mesh, and Hg/Hg₂Cl₂ as anode, cathode, and reference electrode, respectively, under Ar bubbling at a scan rate of 10 mV s⁻¹. The voltage displayed in the figure has been iR‐corrected with measured impedance value. The pH levels of K‐phosphate solutions were adjusted to 7.0 at 25 °C prior to the measurements.