Hematite Surface Modification toward Efficient Sunlight-Driven Water Splitting Activity: The Role of Gold Nanoparticle Addition

Author(s)

Tofanello, Aryane ^[1] ; Freitas, Andre L. M. ^[1] ; Carvalho, Jr., Waldemir M. ^[1] ; Salminen, Turkka ^[2] ; Niemi, Tapio ^[3] ; Souza, Flavio L. ^[1]

Affiliation

^[1] Univ Fed ABC, Lab Alternat Energy & Nanomat, BR-09210580 Sao Paulo - Brazil

^[2] Tampere Univ, Microscopy Ctr, Tampere 33100 - Finland

^[3] Tampere Univ, Photon Lab, FI-33101 Tampere - Finland

• Document type: Journal article
• Source: Journal of Physical Chemistry C; v. 124, n. 11, p. 6171-6179, MAR 19 2020.
• Web of Science Citations: 1

Abstract

Localized surface plasmon resonance has been investigated to enhance light harvesting in hematite-based photoelectrodes modified with gold nanoparticles (AuNPs); meanwhile, an extensive understanding about the different processes involved in the hematite-AuNP system remains unclear. This work addresses a majority of effects associated with AuNP addition by comparing charge transfer, catalytic and light harvesting efficiencies. The obtained results revealed that the lower AuNP amount leads to a higher photocurrent response of 1.20 mA cm(-2) at 1.23 V-RHE in comparison with all photoelectrodes designed here. X-ray photoelectron data revealed that hematite photoelectrodes loaded with higher concentrations of AuNPs immersed in an alkaline electrolyte showed hydrated/oxidized gold phase formation at the electrode/electrolyte interface. This change on the semiconductor-metal interface may affect the conductivity impairing the photocatalytic performance because of the passivation layer on the AuNP surface, decreasing the efficiency of charge transfer. Notoriously, increasing AuNP amount supported on the hematite surface clearly promoted higher light absorption, which was surprisingly not followed by photoelectrochemical efficiency. This result suggests here that the plasmon effect is not a dominant phenomenon that drives the photoelectrode performance. In fact, a deeper analysis showed that the loaded hematite photoelectrodes with low amounts of AuNPs provides a Schottky contact at the semiconductor-metal interface leading to Fermi level equilibration enhancing charge transport efficiency, which is classified as the predominant effect leading to higher photoresponse in the system. (AU)

• FAPESP's process: 14/50516-6 - Enhancing performance of artificial photosynthesis by engineered nanomaterials and photon management
• Grantee: Flavio Leandro de Souza
• Support Opportunities: Regular Research Grants
• FAPESP's process: 16/01000-2 - Effect of metallic nanoparticles in catalytic photoelectric properties of hematite electrodes
• Grantee: Aryane Tofanello de Souza
• Support Opportunities: Scholarships in Brazil - Post-Doctoral