Fig. 4: Chemical oxidation of water during birnessite formation. | Nature Communications

Fig. 4: Chemical oxidation of water during birnessite formation.

From: Cation insertion to break the activity/stability relationship for highly active oxygen evolution reaction catalyst

Fig. 4

a Ir L3-edge XAS spectra probing the reduction of Ir after chemical reaction with KOH. b O2 gas evolution as detected by online mass spectrometry when soaking α-Li1IrO3 in KOH and NaOH solutions with increasing concentrations. c Linear relationship between the amount of intercalated K+ ions in the birnessite phase (as deduced by EDX) and the O2 gas evolution (as deduced from MS). d OER measurements in KOH at pH 14 compared to K2HPO4 at pH 9 demonstrating the K+ deintercalation from the birnessite phase at the OER potential. e Proposed EC mechanism for α-Li2IrO3, involving the electrochemical formation of a high valence α-Li1IrO3 oxide (E step), followed by the chemically oxidation of water to generate O2(g) assisted by K+ intercalation into the birnessite structure (C step).

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