Shaped‐controlled silicon‐doped hematite nanostructures for enhanced PEC water splitting

• Published in: Catalysis today 2019-05, Vol.328, p.43-49
• Main Authors: Allieta, Mattia, Marelli, Marcello, Malara, Francesco, Bianchi, Claudia L., Santangelo, Saveria, Triolo, Claudia, Patane, Salvatore, Ferretti, Anna M., Kment, Štěpán, Ponti, Alessandro, Naldoni, Alberto
• Format: Article
• Language: English
• Subjects: Hematite; Hydrothermal synthesis; Semiconductor; Substitutional doping; Water splitting
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2018.10.010

[Display omitted] •Shape-controlled hematite (a-Fe2O3) nanostructures were fabricated using hydrothermal method.•Different concentration of Si (1÷20 at.%) induced the formation of different crystal shape.•Crystal preferential growth is directed by silicon.•Silicon-doped hematite showed tunable electronic and magnetic properties.•Photoelectrochemical activity of Silicon doped hematite nanocrystals is strongly dependent from their shape. Hematite (α-Fe2O3) is one of the most promising photoanode materials for photoelectrochemical (PEC) water splitting although great challenges hinder high performance. Silicon-doped α-Fe2O3 shows improved PEC activity but the relationship among dopant content and enhanced conductivity, structure, and particle morphology is only poorly understood. Here, we present a systematic study on hydrothermally grown α-Fe2O3 nanocrystals by using XRD, Raman, UV–vis spectroscopy, TEM, XPS, SQUID magnetometry, electrochemical impedance spectroscopy, and photocurrent measurements. We find that the Si content controls the morphology of α-Fe2O3 already at Si 5 at.% inducing a transition from nanostructures with ellipsoidal shape to nanowires. Si doping is effective in improving PEC activity in the case of Si1% at. sample, which shows a 20% photocurrent enhancement in comparison with pure α-Fe2O3. On the contrary, α-Fe2O3 containing Si content higher than 5 at.% presents lower PEC activity. Results are rationalized in the view of the interplay of morphological, structural, magnetic, and electronic properties in doped α-Fe2O3 thus providing general guidelines for the design of efficient photoelectrodes for solar water splitting.