Determining kinetics of H<sub>2</sub>O<sub>2</sub> evolution from photoelectrochemical water oxidation.
basic_science · Level V
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- Record sourced from PubMed, PMID 40849300.
- Also identified by DOI 10.1038/s41467-025-62828-1 and PMC identifier 12375128.
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Abstract
Photoelectrochemical water oxidation to generate H<sub>2</sub>O<sub>2</sub> is a clean and promising method. Its performance is strongly dependent on electrolyte species, in which the Faradaic efficiency is considerably promoted by HCO<sub>3</sub><sup>-</sup> anion. The kinetic mechanism is under debate, which is highly desired but challenging. Herein, we reveal the charge dynamics and reaction kinetics in the H<sub>2</sub>O<sub>2</sub> evolution from photoelectrochemical water oxidation by time-resolved spectroscopic techniques. The H<sub>2</sub>O<sub>2</sub> evolution reaction exhibits the same first-hole transfer dynamics as that in O<sub>2</sub> evolution reaction. The rate law analysis indicates that H<sub>2</sub>O<sub>2</sub> evolution reaction exhibits the first-order reaction kinetics, demonstrating that the rate-determining step in 2e<sup>-</sup> water oxidation reaction for H<sub>2</sub>O<sub>2</sub> evolution is the consumption of the first-hole intermediates. Importantly, the HCO<sub>3</sub><sup>-</sup> anion accelerates the consumption of the first-hole intermediates in 2e<sup>-</sup> water oxidation reaction by about 30 fold in rate constants or 60 fold in turnover frequency relative that in 4e<sup>-</sup> water oxidation reaction. This work sheds light on the control strategy for reaction selectivity by modulation of reaction kinetics in catalysis.