Molten copper hexaoxodivanadate: an efficient catalyst for SO3 decomposition in solar thermochemical water splitting cyclesElectronic supplementary information (ESI) available. See DOI: 10.1039/c3cy00880k

Molten copper hexaoxodivanadate (CuV 2 O 6 ) was identified as an active catalyst for SO 3 decomposition, which is an oxygen generation step in solar thermochemical water splitting cycles, at moderate temperatures ( ca. 600 °C). The SO 3 decomposition over CuV 2 O 6 was significantly accelerated when the reaction temperature approached the melting point ( ca. 630 °C) compared with solid phases of Cu 2 V 2 O 7 as well as other compounds in the CuO-V 2 O 5 system with higher melting points (≥780 °C). A possible intermediate CuSO 4 species formed by SO 3 adsorption onto the Cu oxide site may decompose promptly to evolve SO 2 and O 2 on contact with the molten catalyst phase. Furthermore, the molten catalyst contained a large fraction of monovalent Cu formed by spontaneous desorption of oxygen. A possible reaction mechanism consisting of the fast dissolution of CuSO 4 and Cu 2+ /Cu + redox cycles in the melt is proposed. Molten copper hexaoxodivanadate (CuV 2 O 6 ) was identified as an active catalyst for SO 3 decomposition, which is an oxygen generation step in solar thermochemical water splitting cycles, at moderate temperatures ( ca. 600 °C).