Influence of particle size and shape on the rate of hydrogen produced by Al‐doped SrTiO₃ photocatalysts

Abstract

Photocatalytic hydrogen production rates have been measured from Al‐doped SrTiO3 with a range of controlled shapes and sizes using a high‐throughput parallelized and automated photochemical reactor. It is found that the photocatalytic reactivity is influenced by crystal shape and that crystals with a {1 1 0} to {1 0 0} surface area ratio between 1.3 and 1.8 yield more H2 than crystals with other ratios. Crystals with a {1 1 0}/{1 0 0} surface area ratio of 1.8 generate hydrogen at 550 μmol h−1 g−1 at pH 7, whereas crystals with only {1 0 0} facets exposed generate hydrogen at 300 μmol h−1 g−1 under the same condition. It is likely that the surface area ratio provides the appropriate balance between the photoanodic reaction on the {1 1 0} surface and the photocathodic reaction on the {1 0 0} surface. In the size range of 250–450 nm, larger crystals produce hydrogen at a rate of 400 μmol h−1 g−1 at pH 7, whereas smaller crystals only produce 200 μmol h−1 g−1, suggesting that the larger crystals reduce the rate of electron–hole recombination or back reaction and that the widths of the space charges within the crystal are comparable to the particle radius.

Enabling high ionic conductivity in semiconductor electrolyte membrane by surface engineering and band alignment for LT-CFCs

“…The obtained O-Vacancy formation energy using the vacancy formation equation was 5.2 eV (where STO formation energy is 6.7 eV), according to the previous literature suggesting a higher concentration of O-vacancies [43,44]. The images before and after optimization with the bond lengths have been displayed in the supplementary information (Fig.SI (20)(21)(22)(23)(24)(25)(26).…”

“…It has been used widely for solar cells, batteries, photocatalysis, and fuel cell applications due to its enormously enriched electrical, physical, and optical properties [20]. Also, doping different elements, especially the lower valent such as the Al +3 , La, Nb, Fe, etc., into SrTiO 3 remains a practical approach to enhance the performance by producing abundant O-vacancies of different devices, including photocatalysis and fuel cell [21][22][23][24][25]. Also, in recent years the heterostructure technique has emerged as an exciting area in boosting the performance of fuel cells [26,27].…”

Synthesis and Structure of an Ion‐Exchanged SrTiO3 Photocatalyst with Improved Reactivity for Hydrogen Evolution

“…[ 18 ] Both s‐SrTiO 3 and ix‐SrTiO 3 produce hydrogen at a higher rate at pH 7 than that at pH 2 and 12, which is consistent with our previous work reported for undoped SrTiO 3 single crystals [ 24 ] and Al‐doped SrTiO 3 particles. [ 20 ] This is because the amount of surface charge influences band bending, and pH 7 corresponds to a surface charge where neither the photocathodic nor the photoanodic reaction limit the overall reaction rate. For ix‐SrTiO 3 , the rate is higher in pH 7 water than that in 10% methanol solutions, indicating that the anodic half reaction is no longer the rate‐limiting reaction.…”

“…It has more recently been reported that when SrTiO 3 particles with controlled shapes are heated in molten SrCl 2 , the shapes are preserved. [ 20 ] This suggests that, while some particle erosion or coarsening is possible, the particles do not completely dissolve and recrystallize.…”

Advances in Hybrid Composites for Photocatalytic Applications: A Review

“…In general, the smaller the size of the catalyst nanoparticles, the higher the photocatalytic activity. Cerruto et al systematically correlated the photocatalytic activity to the average sizes and size distributions of TiO 2 nanocrystals [ 41 ], while more recently, the study was extended to the hydrogen produced by Al-doped SrTiO 3 photocatalysts [ 42 ] to the visible photocatalytic activity in β-Bi 2 O 3 [ 42 , 43 ], and the reduction of CO 2 in Cu/Cu 2 O nanocrystals [ 44 ]. The surface properties significantly influence the efficiency of the catalyst because, during the photocatalytic process, oxidation and reduction reactions take place on the surface of the catalyst [ 45 , 46 ].…”