Hematite Nanorods Photoanodes Decorated by Cobalt Hexacyanoferrate: The Role of Mixed Oxidized States on the Enhancement of Photoelectrochemical Performance

Author(s)

Carminati, Saulo Amaral ^[1] ; da Silva, Bruno Leuzinger ^[1] ; Bott-Neto, Jose Luiz ^[1] ; de Melo Jr, Mauricio Alves ; Galante, Miguel Tayar ^[2] ; Fernandez, Pablo Sebastian ^[2] ; Longo, Claudia ^[2] ; Bonacin, Juliano Alves ^[2] ; Nogueira, Ana Flavia ^[2]

Affiliation

^[1] Univ Campinas UNICAMP, Inst Chem, BR-13083970 Campinas, SP - Brazil

^[2] de Melo Jr, Jr., Mauricio Alves, Univ Campinas UNICAMP, Inst Chem, BR-13083970 Campinas, SP - Brazil

• Document type: Journal article
• Source: ACS APPLIED ENERGY MATERIALS; v. 3, n. 10, p. 10097-10107, OCT 26 2020.
• Web of Science Citations: 0

Abstract

In this work, we report on the incorporation of cobalt hexacyanoferrate (Co-NC-Fe) with different iron oxidation states (Fe-II and Fe-III) on hematite (alpha-Fe2O3) nanorod photoanodes with a systematic investigation of enhanced photoelectrochemical performance under a neutral pH. A detailed investigation using in situ techniques was carried out to understand the fundamental aspects of chemical reactions during photoelectrochemical characterization. The alpha-Fe2O3/Co-NC-Fe photoanodes showed a higher photoelectrochemical performance compared to the individual materials. Despite the higher achieved performance of alpha-Fe2O3/Co-NC-Fe, the elucidation of the main contribution upon Co-NC-Fe incorporation was found to be dependent on the different charge transfer mechanism under light illumination. Therefore, given the complexity of the redox processes that take place in Co-NC-Fe under an applied bias, we have systematically investigated the dark- and light-induced effects on alpha-Fe2O3/Co-NC-Fe by in situ UV-vis and Fourier transform infrared spectroscopies. These techniques allowed us to monitor the effect of the electro and photoelectrochemical potential in several redox processes. The insightful results indicate that, in addition to surface state modification effects, the improvement of the photocurrent density may also result from long-lived holes at the electrode surface as a consequence of the electron transfer from the conduction band alpha-Fe2O3 to Co-NC-Fe with a Fe-III oxidation state. This indicates a second electron pathway during charge separation, thereby contributing to the increase in the electron-hole pair lifetime and the accumulation of photogenerated holes at the alpha-Fe2O3/Co-NC-Fe photoanode surface to drive water oxidation. (AU)

• FAPESP's process: 15/23775-3 - Metal oxides nanocomposites with reduced graphene oxide for water splitting reactions and photocatalytic reduction of CO2
• Grantee: Saulo Do Amaral Carminati
• Support type: Scholarships in Brazil - Doctorate
• FAPESP's process: 18/20952-0 - Applied and fundamental studies of the electrochemical conversion of alcohols and CO2
• Grantee: Pablo Sebastián Fernández
• Support type: Program for Research on Bioenergy (BIOEN) - Regular Program Grants
• FAPESP's process: 17/11986-5 - Research Division 1 - dense energy carriers
• Grantee: Ana Flávia Nogueira
• Support type: Research Grants - Research Centers in Engineering Program
• FAPESP's process: 17/23960-0 - Study of the mechanism of water oxidation by catalysts operating at pH7 and its incorporation in electrodes printed in 3D
• Grantee: Juliano Alves Bonacin
• Support type: Regular Research Grants