Gas-Phase Hydroxyl Radical Emission in the Thermal Decomposition of Lithium Hydroxide

The gas-phase hydroxyl (OH) radical emission was observed in the thermal decomposition of lithium hydroxide (LiOH). This phenomenon was investigated in a vacuum flow tube reactor at around 2 Torr by the temperature programmed reaction (TPR) experiments at 500−1300 K. The production of OH and other gaseous products was quantitatively investigated by the laser induced fluorescence method and quadrupole mass spectrometry, respectively. The TPR spectra of OH had a peak at 1100−1200 K, which largely exceeded the gas-phase thermodynamic equilibrium. The origin of OH was supposed to be either the surface OH groups on Li<INF>2</INF>O or the residual LiOH in the LiOH/Li<INF>2</INF>O solid solution. OH production exceeding the thermodynamic equilibrium was explained by means of the partial equilibrium in the reaction:  LiOH + ¹/<INF>4</INF>O<INF>2</INF>  ¹/<INF>2</INF>Li<INF>2</INF>O + OH. This phenomenon can be a new route for the OH production from H<INF>2</INF>O and O<INF>2</INF> in cyclic reactions of lithium compounds.