Unraveling the impact of tetravalent and pentavalent ions on the charge dynamics of hematite photoelectrodes for solar water splitting

Author(s)

Lima, Brenda R. ; Rodriguez-Gutierrez, Ingrid ; Verissimob, Nathalia C. ; Albuquerque, Angela ; Santos, Gabriel T. ; Bettini, Jefferson ; Souza, Flavio L.

• Document type: Journal article
• Source: MATERIALS TODAY CHEMISTRY; v. 34, p. 12-pg., 2023-11-02.

Abstract

This study focuses on understanding the impact of tetravalent (Hf4+) and pentavalent (Nb5+) ions in hematite photoelectrodes using a two-step synthesis approach. Structural, morphological, and compositional analyses confirms that Nb5+ is segregated over the hematite crystal surface while Hf4+ is allocated over the crystal surface and between the fluorine-doped tin oxide substrate (FTO)-hematite interface. Our results indicate that the modifier insertion led to substantial improvements in overall efficiency and photoelectrochemical (PEC) performance. However, it creates additional surface states, as evidenced by shifts in the anodic onset potential (Vonset) observed in the linear sweep voltammetry curves. For Nb-modified photoelectrodes, Vonset shift of-20 mV with respect to hematite was observed and confirmed by intensity modulated photocurrent spectroscopy (IMPS). For Hf-modified hematite, this Vonset shift is more pronounced (-30 mV). When combined with NiFeOx, Nb5+ acted synergistically showing a 4-fold efficiency increase compared to hematite and-70 mV cathodic shift in the Vonset. Otherwise, NiFeOx showed no significant impact in the Hf4+ modified hematite photoelectrodes, suggesting that Hf4+ role lies in enhancing electron collection at the FTO-hematite interface. This study not only sheds light on the charge dynamics of modified hematite photoelectrodes but also provides strategies for boosting the PEC devices efficiency. (AU)

• FAPESP's process: 17/02317-2 - Interfaces in materials: electronic, magnetic, structural and transport properties
• Grantee: Adalberto Fazzio
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 19/24394-4 - Boosting hematite photoelectrode water splitting activity by dopant addition
• Grantee: Brenda Raffaela de Lima
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 19/06654-9 - Incorporation of metallic nanoparticles in hematite photoelectrodes: effect of solid-solid interface on optical and electrical properties
• Grantee: Ingrid Guadalupe Rodriguez Gutierrez
• Support Opportunities: Scholarships in Brazil - Post-Doctoral