Strategic usage of redox active materials and sacrificial Zn electrodes for spontaneous hydrogen evolution reaction

Abstract

The availability of renewable energy in conventional water electrolysis is random and inefficient. Therefore, exploring the use of efficient materials and designs to improve the performance and durability of electrolysis in renewable energy systems makes it a promising and sustainable solution for green-hydrogen production. Here, the idea of strategically using a redox active material (RAM) as a mediator for storing energy chemically in conjunction with efficient water electrolysis is explained in this study. Another strategy is to use a sacrificial electrode and a RAM to address the disadvantage of traditional water splitting using external energy. The chosen RAM, 2,5-dihydroxy-1,4-benzoquinone (DHBQ), has high solubility, low cost, reversibility, and negative potential in aqueous systems. The spontaneous hydrogen evolution reaction (HER) module was designed based on the standard reduction potential difference between DHBQ and the HER, confirming a maximum power density of 43.12 mW cm⁻² at 100 mA cm⁻². The oxygen evolution reaction (OER) and the Zn module showed efficient energy utilization in the DHBQ reduction tests. Comparative experiments with an alkaline water electrolyser (AEMWE) and an acidic water electrolyser (CEMWE) vs. our OER–HER system revealed a total energy consumption of 30.4% lower than the average of others, demonstrating efficient energy use. Moreover, both modules achieved spontaneous operation in the complete system with the Zn sacrificial electrode, resulting in a maximum power density of 40 mW cm⁻² for the Zn module and 43.12 mW cm⁻² for the HER module. Overall, the demonstrated energy output was 1.85 W h per LH₂. This innovative approach ensures the utilization of components and reduces power consumption, making it a promising solution for sustainable hydrogen production.