Hydrogen is an important chemical and energy source, which is widely used in a number of key industrial processes such as desulfurization of petroleum, ammonia and Fischer-Tropsch synthesis and as a critical fuel in low temperature fuel cells fuel cells. Electrolysis of water is a promising electrochemical process that generates clean hydrogen from water. Conventional low-temperature water electrolyzers, for most part, are limited from low efficiencies. On the other hand, much higher efficiencies can be obtained when utilizing high temperature electrolyzers such as solid oxide electrolyzers (SOE). The efficiency of the current SOE systems can be significantly increased if the overpotential losses at the SOE electrodes are minimized.In this contribution, we have employed quantum density functional theory (DFT) calculations along with experimental electrochemical, spectroscopic and microscopic techniques to obtain a fundamental understanding of the chemical transformations that govern the overpotential losses associated with the electrochemical water splitting at the SOE cathodes. Our calculations show that on Ni cathode electrocatalysts, as the applied potential increases, the oxygen coverage at the cathode decreases and the number of empty active surface sites available to activate the rate-limiting step increases, leading to higher rates for the electrochemical water splitting. Our theoretical DFT findings are supported by our experimental results.

Fundamental insights on the electrochemical water splitting using solid oxide electrolyzers

245th National Meeting (2013)

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