Activating the surface and bulk of hematite photoanodes to improve solar water splitting

• Published in: Chemical science (Cambridge) 2019-11, Vol.1 (44), p.1436-1444
• Main Authors: Zhang, Hemin, Park, Jong Hyun, Byun, Woo Jin, Song, Myoung Hoon, Lee, Jae Sung
• Format: Article
• Language: English
• Subjects: Activation; Anodizing; Chemistry; Electrochemical activation; Hematite; Nanorods; Oxidation; Photoanodes; Photoelectric effect; Photoelectric emission; Scanning; Water splitting
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c9sc04110a

A simple electrochemical activation treatment is proposed to improve effectively the photoelectrochemical performance of Nb,Sn co-doped hematite nanorods. The activation process involves an initial thrice cathodic scanning (reduction) and a subsequent thrice anodic scanning (oxidation), which modifies both the surface and bulk properties of the Nb,Sn:Fe 2 O 3 photoanode. First, it selectively removes the surface components to different extents endowing the hematite surface with fewer defects and richer Nb-O and Sn-O bonds and thus passivates the surface trap states. The surface passivation effect also enhances the photoelectrochemical stability of the photoanode. Finally, more Fe 2+ ions or oxygen vacancies are generated in the bulk of hematite to enhance its conductivity. As a result, the photocurrent density is increased by 62.3% from 1.88 to 3.05 mA cm −2 at 1.23 V RHE , the photocurrent onset potential shifts cathodically by ∼70 mV, and photoelectrochemical stability improves remarkably relative to the pristine photoanode under simulated sunlight (100 mW cm −2 ). Waking up the hematite lion: a simple electrochemical activation treatment leads to surface passivation outside and generation of oxygen vacancies inside, which greatly enhances photoelectrochemical water splitting.