Aluminum enhances photochemical charge separation in strontium titanate nanocrystal photocatalysts for overall water splitting. Issue 33 (8th August 2018)

• Record Type: Journal Article
• Authors: Zhao, Zeqiong; Willard, Emma J.; Li, Hui; Wu, Zongkai; Castro, Ricardo H. R.; Osterloh, Frank E.
• Is Part Of: Journal of materials chemistry. Volume 6:Issue 33(2018)
• Page Start: 16170
• Page End: 16176
• Publication Date: 2018-08-08
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c8ta05885g
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : Photovoltage and overall water splitting activity of nanocrystals of aluminium-doped SrTiO3 correlate with aluminum content. Abstract : Strontium titanate (SrTiO3 ) is a well-known photocatalyst for overall water splitting (OWS) under ultra-violet irradiation. Recently, it was shown that Al-doped SrTiO3 microparticles prepared by flux-mediated solid-state reaction catalyze OWS with an apparent quantum efficiency of 30% at 360 nm, the highest value reported so far for strontium titanate. However, the roles of Al 3+ and of the particle morphology in controlling the activity are not clear. Here we report a new synthetic route to well defined nanocrystals of Al:SrTiO3 with controllable Al-concentration (3–8 atom%) using TiO2, Sr(OH)2 and Al(NO3 )3 as starting materials. X-Ray diffraction and transmission electron microscopy confirm the presence of perovskite-type cubic nanoparticles with size of 60 nm. After loading with a Rh2− y Cr y O3 cocatalyst, nano-Al:SrTiO3 catalyzes OWS under UV/vis illumination from a Xe lamp. The activity shows a volcano-like dependence on Al concentration, confirming that Al 3+ content is a key factor for the activity. Nanocrystals doped with 7.2 atom% Al show the activity of 53 μmol H2 per hour under 240 mW cm −2 UV illumination and an AQE of 0.06% at 375 nm. Based on surface photovoltage spectroscopy (SPS), aluminum enhances photochemical charge separation in the Al:SrTiO3 nanocrystals and reduces electron and hole trapping. However, under UV/vis illumination, the Al:SrTiO3 nanocrystals are found to be 40 times less active than Al:SrTiO3 microparticles made by flux reaction in SrCl2 . The lower activity of the nanoparticles is due to optical shielding from the Rh2− y Cr y O3 co-catalyst.