Negative Impact of Surface Ti3+Defects on the Photocatalytic Hydrogen Evolution Activity

Electronic Supporting Information

Negative impact of surface Ti3+defects on the photocatalytic hydrogen evolution activity of SrTiO3

Haidong Chen1,Feng Zhang1,2,*, Weifeng Zhang1,2, Yingge Du3, Guoqiang Li1,2,*

1. Henan Key Laboratory of Photovoltaic Materials, Henan University, Kaifeng 475004, P.R. China.

2. Laboratory of Low-dimensional Materials Science, Henan University, Kaifeng 475004, P.R. China.

3. Physical Sciences Division, Pacific Northwest NationalLaboratory, Richland, WA, 99352 USA.

*Corresponding authors. E-mail addresses:

1. Experimental

Commercial SrTiO3 powders (99.99%, Aladdin Industrial Corporation) were used in our experiment. The commercial powder was confirmed as pure phase of SrTiO3 by an X-ray diffractometer (DX-2700 diffractometer, Fangyuan) with CuKα radiation (λ= 0.154145 nm) in θ–2θ mode.The commercial SrTiO3 was annealed at 1273 K in a tube furnace for 10, 20 and 40h. For some control experiments, it was annealed at 973 and 1173K for 40h.

The electron paramagnetic resonance (EPR) of the samples was recorded at room temperature on a JES-FA200 electron spin resonance spectrometer.In the case of X-ray photoelectron spectroscopy (XPS) (Thermo ESCALAB 250), an Al anode with a monochromator was used to significantly reduce the background signal. The binding energy was referenced to the C 1s peak taken at 284.8 eV. We used the XPS Peak Processing analysis the XPS results of O1s with the same function (10% Lorentzian-Gaussian).

The photocatalytic hydrogen evolution was carried out at room temperature as the following process. The powder photocatalyst (0.1 g) was dispersed into 100ml 25 vol% aqueous methanol solution in a 300ml glass reactor with the concentration of H2PtCl6 (25.6μg/L). In some control experiments, the system was purged with N2 for 30 min before the light irradiation. After being sealed, the reactor was placed before a 300W Xe lamp with a fixed distance. The stirring is on during the reaction. The amount of H2 evolved was determined using an off-line gas chromatography (GC1690, Kexiao Ltd. China).

2. Results

Figure S1. (a) XRD patterns of the sample annealed at 1273K for 0, 10, 20 and 40h. (b) FWHM of the main peak, (c) the enlarged view of the main peak at 32.5o.

Figure S2.Ti 2p XPS line of the sample annealed at 1273K for 0, 10, 20 and 40h.

Figure S3.(a) Uv-vis diffusion spectra of the sample annealed at 1273K for 10, 20 and 40h. (b) The PL spectra of the samples annealed at 1273K for 10 and 40h.

Figure S4.TGA curve of the sample annealed at 1273K for 20h (red) and original STO(black).

The weight of original STO will decrease with increasing the temperature. The weight of sample annealed at 1273k for 20h will increase between 150 and 450oC due to the oxygen defect reacting with the oxygen.[Nanoscale 8, 16963 (2016)]

Figure S5. (a) Photocatalytic H2 evolution from the aqueous methanol solution (25ml of CH3OH, 75ml of H2O) over SrTiO3annealed at 1273K for 0, 10, 20 and 40h with 26.5μg/L of H2PtCl6 solution in ambient air. (b) the induction time obtained from the sample annealed at 1273K for 10, 20 and 40h.

Figure S6. Photocurrent result in 0.5M Na2SO4 aqueous solution.

Figure S7. Surface Pt:Ti atomic ratio obtained from the sample annealed at 1273K for 10, 20 and 40h after reaction.

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