NOVELTY - A hydrogen production apparatus comprises a reaction medium (102), an anode (106) in contact with the reaction medium, a cathode (104) in contact with the reaction medium and in conductive contact with the anode, and a catalyst suspended in the reaction medium. The catalyst has a high surface-area-to-volume ratio.    USE - For producing hydrogen gas used in generation of electric potential.    ADVANTAGE - The inventive apparatus enables efficient production of hydrogen gas using inexpensive metals.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a battery comprising a reaction medium, a first metal in contact with the reaction medium, a first electrode comprising or in conductive contact with the first metal, a second metal in contact with the reaction medium, a second electrode comprising or in conductive contact with the second metal, and a catalyst suspended in the reaction medium and having a high surface-area-to-volume ratio;    (2) production of hydrogen gas by suspending a colloidal metal in a reaction medium, contacting the reaction medium with a cathode, contacting the reaction medium with an anode, and electrically connecting the cathode and the anode;    (3) a method of controlling the production of hydrogen by suspending a colloidal metal in a reaction medium, contacting the reaction medium with a cathode, contacting the reaction medium with an anode, connecting the cathode and the anode via a conductive path, and varying the resistance along the conductive path; and    (4) an electrical power generator comprising a reaction vessel, a reaction medium contained within the reaction vessel, an anode in contact with the reaction medium, a cathode in contact with the reaction medium and in conductive contact with the anode, a catalyst metal in contact with the reaction medium and being in colloidal form or having a surface-area-to-volume ratio of greater than or equal to2.98x108 m2/m3, an outlet in the reaction vessel to allow hydrogen gas to escape from the reaction vessel, and a fuel cell to accept hydrogen from the outlet and use the gas to produce an electric potential.    DESCRIPTION OF DRAWING(S) - The figure is a diagram of the inventive hydrogen production apparatus.    Reaction vessel (100)    Reaction medium (102)    Cathode (104)    Surface-area-increasing features (105)    Anode (106)    Conductive paths (107, 109, 116, 118)    Controller (108)    Electrical power source (114)    First and second terminals (115, 117)    Energy source (122)