Hydrothermal synthesis of CuV₂O₆ supported on mesoporous SiO₂ as SO₃ decomposition catalysts for solar thermochemical hydrogen production

Hydrothermal synthesis of CuV₂O₆ supported on 3-D ordered mesoporous SiO₂ (CuV/SiO₂) was studied to evaluate the catalytic activity for SO₃ decomposition, which is a key step in solar thermochemical hydrogen production. A composite oxide hydrate, Cu₃O(V₂O₇)·H₂O, and an oxide hydroxide hydrate, Cu₃(OH)₂V₂O₇·(H₂O)₂, were formed at lower hydrothermal temperatures (≤200 ). The oxide hydrate phase mainly yielded Cu after calcination at 600 in air. By contrast, the hydrothermal synthesis at 250 (CuV/SiO250) directly crystallized CuV from the oxide hydroxide hydrate, although its very large particle size (∼5 μm) is not suitable for the catalytic application. The SO decomposition activity measured at 600 was associated with the yield as well as the dispersion of CuV, giving rise to the maximum for the hydrothermal synthesis at 200 CuV/SiO250 achieved the highest catalytic activity at the reaction temperature of 650, because the melting phase of CuV penetrated mesoporous SiO and thus improved the dispersion of the active phase.