An electron spin resonance study on the Re/ZrO2 system

Abstract

The clear room-temperature e.s.r. signal observed for a Re/ZrO₂ catalyst at 9.5 GHz has been analysed to obtain the following values for the e.s.r. parameters g_xx= 1.76, g_yy= 1.83, g_zz= 1.96, |A|_xx= 17.1 mT, |A|_yy= 45.2 mT and |A|_zz= 91.6 mT. The analysis has revealed that hexavalent rhenium cations (5d¹, I= 5/2, S=½) are responsible for the e.s.r. signal observed. A qualitative discussion both of the crystal field around the rhenium cation and of the O^–₂ e.s.r. signal observed for the oxidized sample is presented.