Dynamic charge collecting mechanisms of cobalt phosphate on hematite photoanodes studied by photoinduced absorption spectroscopy

Reaction sites, surface states, and surface loaded electrocatalysts are photoinduced charge storage sites and critical to photoelectrochemical (PEC) performance, however the charge transfer mechanisms involved in the three remain poorly understood. Herein, we studied the charge transfer processes in...

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Bibliographic Details
Published in:Chemical science (Cambridge) 2023-02, Vol.14 (7), p.1861-187
Main Authors: Li, Dongfeng, Wei, Ruifang, Yin, Heng, Zhang, Hemin, Wang, Xiuli, Li, Can
Format: Article
Language:English
Subjects:
Absorption spectroscopy
Charge transfer
Chemistry
Cobalt
Electrocatalysts
Hematite
Oxidation
Photoanodes
Separation
Spectrum analysis
Surface chemistry
Valence band
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Summary:Reaction sites, surface states, and surface loaded electrocatalysts are photoinduced charge storage sites and critical to photoelectrochemical (PEC) performance, however the charge transfer mechanisms involved in the three remain poorly understood. Herein, we studied the charge transfer processes in hematite (Fe 2 O 3 ) without/with loaded cobalt phosphate (CoPi) by operando photoinduced absorption (PIA) spectroscopy. The loaded CoPi receives trapped holes in surface states at low potential and directly captures holes in the valence band at high potential. Through the dynamic hole storage mechanisms, loaded CoPi on Fe 2 O 3 facilitates spatial charge separation and serves as a charge transfer mediator, instead of serving as a catalyst to change the water oxidation mechanism (constant third-order reaction). The spatial separation of photoinduced charges between Fe 2 O 3 and CoPi results in more long-lived holes on the Fe 2 O 3 surface to improve PEC water oxidation kinetically. The dynamic charge collecting mechanism sheds light on the understanding and designing of electrocatalyst loaded photoanodes. Loaded CoPi on Fe 2 O 3 facilitates spatial charge separation by dynamic hole storage mechanisms, in which CoPi receives trapped holes in surface states at low potential and directly captures holes in the valence band at high potential.
ISSN:2041-6520
2041-6539
DOI:10.1039/d2sc05802b