## 2 Materials and Methods  
### Synthesis of Rh-Doped SrTiO\({}_{3}\) with Ru Cocatalyst for H\({}_{2}\) Evolution  
Two different titanium precursors, anatase TiO\({}_{2}\) (Alfa aesar) and TiCl\({}_{4}\) Alfa aesar), were used in the microwave-assisted hydrothermal synthesis of Rh-doped SrTiO\({}_{3}\).  
The Rh-doped SrTiO\({}_{3}\) prepared by anatase TiO\({}_{2}\), MW-STO2 Rh-A, were synthesized by using anatase TiO\({}_{2}\), Sr(OH)\({}_{2}\) and Na\({}_{3}\)RhCl\({}_{6}\) as starting materials, where the molar composition of Ti:Sr:Rh was 100:98:2. The starting materials was added to 30 mL of 5M NaOH aqueous solution in sequence under vigorous stirring. Then, the start material was transferred to a 100 cm\({}^{3}\) Teflon autoclave and the microwave-assisted hydrothermal treatment was performed in a commercial microwave digestion system (StartD, Milestone, Taiwan, 2011). The microwave hydrothermal process was performed at 180 \({}^{\circ}\)C for 1 h. After synthesis reactions, the product was washed by distillated H\({}_{2}\)O and dried at 60 \({}^{\circ}\)C overnight.  
The Rh-doped SrTiO\({}_{3}\) prepared by TiCl\({}_{4}\), referred as MW-STO2 Rh-T, were synthesized by a similar procedure: TiCl\({}_{4}\), 1 M solution in toluene (Sigma-Aldrich, used as purchased), Sr(OH)\({}_{2}\) and Na\({}_{3}\)RhCl\({}_{6}\) were used as starting materials where the molar composition of Ti:Sr:Rh was 100:98:2. The color of MW-STO2 Rh-A and MW-STO2 Rh-T varies from light yellow-green to gray-green. The color of samples became darker with increasing Rh amount.  
In this study, conventional hydrothermal synthesis and solid-state synthesis of Rh-doped SrTiO\({}_{3}\) photocatalyst, denoted as HT-STO2 Rh, and SS-STO2 Rh were also prepared by for comparison. The HT-STO2 Rh were synthesized by using anatase TiO\({}_{2}\), Sr(OH)\({}_{2}\) and Na\({}_{3}\)RhCl\({}_{6}\) where the molar ratio of Ti:Sr:Rh= 100:98:2. The starting materials was added to 30 mL of 5M NaOH aqueous solution in sequence under vigorous stirring. The precursor solution was transferred to a 100 cm\({}^{3}\) Teflon lined autoclave. Then, the hydrothermal synthesis was carried out at 180 \({}^{\circ}\)C for 24 h. The HT-STO2 Rh showed a similar color to that of MW-STO2 Rh-A and MW-STO2 Rh-T.  
The SS-STO2 Rh were prepared a two-step solid-state reaction using anatase TiO\({}_{2}\), SrCO\({}_{3}\), Rh\({}_{2}\)O\({}_{3}\) (molar ratio 100: 98: 1). The mixed precursor was calcinated in air at 1273 K for 10h then at 1273 K for 10 h with an intermediate grinding process between the two calcinations; essentially similar of the procedure by [PERSON] et al. (20). The color of SS-STO2 Rh was black.  
Ru nanoparticles were used as a H\({}_{2}\) evolution cocatalyst and were loaded on Rh-doped SrTiO\({}_{3}\) by photo-deposition method. Rh-doped SrTiO\({}_{3}\) and an aqueous solution RuCl\({}_{3}\):xH\({}_{2}\)O (1 wt % Ru loading for complete photoreduction) were added to a methanol solution (vol. ratio of MeOH:H\({}_{2}\)O = 1:10). The suspension was irradiated in a photoreactor with a 400 W medium-pressure metal halide lamp (Phillips HPA400) for 12 h under string at room temperature. The sample was then filtered and washed with distilled water. Finally, the photocatalyst was dried at 60 \({}^{\circ}\)C overnight.