The electrochemical behavior of hydride ion at a molybdenum electrode in a LiBr-KBr-CsBr-LiH melt has been studied by cyclic voltammetry and chronopotentiometry. The obtained voltammograms and chronopotentiograms were classified as a reversible system. The electron number was found to be one. It was found that hydride ion was anodically oxidized at around 0.50 V vs. Li+/Li and pure hydrogen gas was generated according to the following reaction H- --> 1/2H(2) 1 e. Using voltammetry and chronopotentiometry diffusion coefficients of hydride ion were estimated as 1.2 x 10(-1) exp(-4.5 x 10(4)/RT) cm(2) s(-1) at 523-673 K. (C) 2003 The Electrochemical Society.