Effects of coexisting oxoanions on SO3 decomposition activity of molten-phase potassium metavanadate catalysts

Molten-state potassium metavanadate (KVO3) supported on mesoporous SiO2 materials have emerged as active catalysts for SO3 decomposition over a moderate temperature range ( over line 650 degrees C), which is a potential O2 evolution reaction useful for solar thermochemical water splitting. The molten phase formed at 2520 degrees C contained tetrahedral VO42-, which plays a vital role in accelerating the SO3 uptake and conversion to SO2/O2. The present study aimed to reveal how the SO3 decomposition activity is affected by adding other oxoanions such as borate (BO33-), carbonate (CO32-), and phosphate (PO43-) into the melt. Although borate showed a deteriorating effect, phosphate tended to improve the catalytic activity when the P/V molar ratio was equal to or less than 0.5. The addition of phosphate produced a mixed phosphate vanadate with a composition of KV2PO8, which consists of infinite tetrahedral PO4 and pyramidal VO5 linked by vertex sharing. Because of the congruent melting at temperature as low as 3530 degrees C, KV2PO8 may be expected as another candidate of active molten phase catalyst for SO3 decomposition. (c) 2022 The Ceramic Society of Japan. All rights reserved.

Automated summary

Molten-state potassium metavanadate supported on mesoporous SiO2 materials is an active catalyst for SO3 decomposition, and the addition of phosphate can enhance its catalytic activity and form mixed phosphate vanadate KV2PO8.