Sulfuric acid decomposition on the Pt/n-SiC catalyst for SI cycle to produce hydrogen

•The n-SiC with high surface area was prepared using SiO2.•A Pt/n-SiC catalyst showed the high activity and stability for sulfuric acid decomposition.•The surface of n-SiC was covered by oxidized Si.•The surface oxidized Si stabilized the Pt particles on the n-SiC.

The sulfuric acid decomposition should be performed in the wide temperature ranges from 550 °C to 950 °C to absorb the sensible heat of He in SI process. Therefore, the catalysts for the reaction should be stable even in the very corrosive reaction condition of 650 °C. Here, the Pt/n-SiC catalyst was prepared for the purpose and compared with the Pt/SiC catalyst. The both catalysts showed the high stability in the temperature ranges from 650 to 850 °C. The n-SiC with the surface area of 187.1 m2/g was prepared using nano-sized SiO2, which resulted in amorphous SiC phase. The SiC support with the surface area of 19.2 m2/g for the comparison showed the well crystalline structure. In spite of the large surface area differences between the n-SiC and SiC support, the Pt particle sizes of the Pt/n-SiC (average Pt size: 26.4 nm) catalyst were not so much different from those of the Pt/SiC (average Pt size: 26.1 nm) catalyst after the calcination at 1000 °C for 3 h. However, the catalytic activity of the Pt/n-SiC was much higher than that of the Pt/SiC. XRD analysis indicated that the Pt particles on the Pt/n-SiC was more stable than those of the Pt/SiC in the sulfuric acid decomposition and XPS analysis showed that the Pt valence state on the Pt/n-SiC was higher than that on the Pt/SiC. The surface analysis showed that the surface of the n-SiC particles was covered by SiO2 and Si4C4−xO4. These experimental results indicate that the Pt metal particles on n-SiC were stabilized on the oxidized Si surface. Therefore, it is suggested that the Pt particles stabilized on the oxidized Si surface can be a reason for the higher activity of the Pt/n-SiC catalyst as compared with the Pt/SiC catalyst.

Graphical abstractSulfuric acid decomposition with respect to reaction time at 650 °C (▵, ▲), 750 °C (○, ●), 850 °C (□, ■) and a GHSV of 76,000 mL/gcat/h: open symbols for Pt/SiC catalysts and filled symbols for Pt/n-SiC.Figure optionsDownload full-size imageDownload as PowerPoint slide