杂多酸的XPS研究(Ⅲ)——钼钒杂多酸热稳定性的研究

XPS STUDIES ON HETEROPOLYACIDS (Ⅲ) STUDY ON DIFFERENCE IN THERMOSTABILITY BETWEEN MOLYBDIC AND VANADIC HETEROPOLYACIDS

用XPS测定了PMo_(12-n)V_n、PV_(14)中O_(1S)、P_(2p_(3/2))、Mo_(3d_(5/2))的结合能、结合差热及红外数据,研究了钼、钒Keggin型杂多酸的热稳定性,并与钨、钼杂多酸的热稳定性进行了比较。结果表明,与钨、钼杂多酸相比,钼、钒杂多酸之间O_(1S)结合能及其热稳定性有较大的变化。由此可推测,钼、钒杂多酸的热稳定性主要受金属—氧的轨道重叠程度、杂多阴离子的电荷及M-O-M键角等因素的影响。

The binding energies of O_(1s), P_((2p)_(3/2)), Mo_((3d)_(5/2)) and V_((2p)_(3/2)) in PMo_(12-n) V_n and PV_(14) were determined by XPS. Referring to the TG-DTA and IR data, the difference in thermostability between PMo_(12) and PV_(14) was researched into, and compared with that between PW_(12) and PMo_(12).The results show that there is more difference of O_(1S) binding energy and thermostability of heteropolyacids between PMo_(12) and PV_(14) than that between PW_(12) and PMo_(12). It is deduced that the difference in thermostability between PMo_(12) and PV_(14) was mainly decided by such factors as the overlap of metal and oxygen orbitals, the charges of heteropoly-anions and the bond angle of M-O-M.