The reduced forms of heteropolyacids (HPA) in acidic aqueous solutions are capable of spontaneous reoxidation, releasing H/sub 2/, as is reported elsewhere. It can therefore be expected that the reduced forms of HPAs with negative electrochemical reduction potentials E /SUB o/ should also release H/sub 2/ in the presence of metallic catalysts. Feasibility in principle has also been demonstrated for the use of colloidal Pt to catalyze the generation of H/sub 2/ from solutions of reduced forms of 12-tungstosilicic HPA. In this paper the authors report on their study of the evolution of H/sub 2/ from solutions of reduced forms of this HPA in the presence of the heterogeneous Rh polymer catalyst Rh-AN-221, which is active in the reaction of hydrogen generation from acidic aqueous solutions of the one-electron reducing agents V/sup 2 +/ (aq) and Cr/sup 2/(Aq).