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Expediting hole transfer via surface states in hematite-based composite photoanodes
Lili Gao1, Peng Wang1, Huan Chai1
1State Key Laboratory of Applied Organic Chemistry (SKLAOC), The Key Laboratory of Catalytic Engineering of Gansu Province, Key Laboratory of Advanced Catalysis of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China. majiantai@lzu.edu.cn.
This study reveals that surface states in CoCr layered double hydroxide (LDH)/Fe2O3 composite photoanodes can act as hole transfer stations, improving charge transport. Zr doping enhances current density but can shift onset potential, highlighting the importance of surface state modulation for efficient photoanodes.
Area of Science:
- Materials Science
- Electrochemistry
- Surface Chemistry
Background:
- Hematite (Fe2O3) photoelectrodes typically rely on Fe(IV)=O states for hole transfer, with other surface states acting as recombination centers.
- The role of recombining surface states in charge transport within modified photoelectrodes is underexplored.
- Understanding charge transfer pathways is crucial for optimizing photoanode performance in energy conversion applications.
Purpose of the Study:
- To investigate distinct charge transfer pathways in CoCr layered double hydroxide (LDH)/Fe2O3 and CoCr LDH/Zr:Fe2O3 composite photoanodes.
- To explore the role of surface states, particularly recombining surface states (r-SS), in modified photoelectrode performance.
- To elucidate the impact of Zr doping and cocatalyst modification on charge dynamics and photoanode efficiency.
Main Methods:
- Fabrication and characterization of CoCr LDH/Fe2O3 and CoCr LDH/Zr:Fe2O3 composite photoanodes.
- Electrochemical measurements to analyze charge transfer and recombination dynamics.
- Investigation of surface state properties and their influence on photoelectrochemical performance.
Main Results:
- In composite photoanodes, recombining surface states (r-SS) function as hole transfer stations, inducing high-valent Co cations and determining onset potential.
- Fe(IV)=O states remain active intermediates for hole transport to cocatalysts, enhancing charge utilization efficiency.
- Zr doping increases active Fe(IV)=O states, boosting current density but causing a delayed onset potential due to shifted surface states.
Conclusions:
- Surface state distribution significantly influences anisotropic charge transfer and recombination in composite photoanodes.
- Surface states, including r-SS, play a dual role, acting as both recombination centers and hole transfer pathways depending on the material composition.
- Modulating surface states through dopants (Zr) and cocatalysts (CoCr LDH) is a key strategy for optimizing composite photoanode design and performance.
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