Evaluation of the Catalytic Effect of Metal Additives on the Performance of a Combined Battery and Electrolyzer System

A low-cost method of green hydrogen production via the modification of a lead acid battery has been achieved, resulting in a hydrogen flow rate of 5.3 L min^–1 from a 20-cell string. The electrochemical behavior and catalytic effect of various metal additives on the hydrogen evolution reaction (HER) was evaluated using cyclic voltammetry. Nickel, cobalt, antimony, manganese, and iron were investigated, with 66 ppm nickel achieving a 75% increase in hydrogen produced from a modified lead acid battery. Design of Experiments (DOE) employing a simple centroid design model to analyze the combined additive effects of nickel, cobalt, and antimony was performed to evaluate the effect on the HER. A combination of Ni:Co:Sb in the ratio 66:17:17 ppm achieved the greatest end voltage shift of the HER from −1.65 to −1.50 V; however, no increase in hydrogen yield was observed in comparison to 66 ppm of nickel when added to a full-scale cell. Gas chromatography using a thermal conductive detector and a sulfur chemiluminescence detector were used to measure the purity of hydrogen obtained from a string of 20 battery electrolyzer cells connected in series. 99% purity hydrogen gas was obtained from the battery electrolyzer cells, with H₂S impurities below the limit of detection (0.221 ppm).