Catalyze hydrolysis reaction for hydrogen generation by Mg/Mg2Ca nanolamellar structure in Mg–Ca alloys

Abstract

The hydrogen generating characteristics of Mg–Ca alloys with Mg/Mg 2 Ca nanolamellar structures in the hydrolysis reaction with artificial seawater—a 3.5-wt% NaCl aqueous solution—were investigated for a new hydrogen supply source application. The concept of this study was to fabricate a complete hydrolysis reaction alloy using nanolamellar structure of Mg and Mg 2 Ca having an electrochemically less noble product than Mg. The hydrolysis reaction properties of Mg-10Ca, Mg-15Ca, Mg-16.2Ca, Mg-20Ca, and Mg 2 Ca were compared with respect to microstructure, which is the volume fraction of the primary phase and its nanolamellar width, and reaction temperatures at 10 °C, 20 °C, 30 °C, 40 °C, 50 °C, and 60 °C. Mg-16.2Ca and Mg-20Ca reacted completely even at room temperature and became white powders comprising Mg(OH) 2 , Ca(OH) 2 , and CaCO 3 after 9–14 days without changing the solvent. The hydrolysis reaction rates of the Mg–Ca alloys in the temperature range of 10–40 °C were fast in the order of Mg-16.2Ca ≥ Mg-20Ca ≥ Mg-10Ca ≥ Mg-15Ca. From the results of the hydrolysis reaction rate dependency on temperature, the activation energies of Mg-10Ca, Mg-15Ca, Mg-16.2Ca, Mg-20Ca, and Mg 2 Ca were estimated to be 41.27, 43.39, 22.07, 15.46, and 29.27 kJ mol −1 , respectively. This study revealed that the eutectic structure with several nanogalvanic cells of Mg/Mg 2 Ca in the alloys accelerated the hydrolysis reaction and completely reacted with artificial seawater for hydrogen generation.