R-009

Andris Šutka

andris.sutka@rtu.lv

Mārtiņš Vanags, Mairis Iesalnieks

Riga Technical University, Latvia

Decoupled membrane-free production of hydrogen using transition metal oxide redox mediators

Hydrogen stands out as a promising energy carrier, capable of reducing carbon emissions and addressing energy demands. Electrolysis provides an efficient means to produce hydrogen, enabling the storage of surplus energy from renewable sources. Nevertheless, the goal of making hydrogen production both cost-effective and widely accessible remains elusive. Traditional water electrolysis systems generate gases concurrently, relying on membranes to separate hydrogen and oxygen and prevent the formation of a hazardous gas mixture. Yet, these membranes come with significant limitations that impede the affordability and broad adoption of hydrogen production. The disadvantages of membrane-based electrolyzers include higher costs, compromised safety, shorter operational lifespans, elevated overpotentials, the need for intricate gas collection setups, restricted energy management flexibility, and the impending prohibition of fluoropolymer-based membrane materials. Additionally, the rate of the hydrogen evolution reaction (HER) is tied to the oxygen production rate, constrained by the slower kinetics of the oxygen evolution reaction (OER).

Separating the OER and HER offers a compelling solution to eliminate the reliance on membranes [1-3], achievable through the use of transition metal oxide redox mediators. In decoupled water electrolysis (DWE), the OER and HER are performed independently in terms of both space and time, facilitated by a metal oxide redox mediator. The success of DWE in hinges on the properties of the redox mediators, particularly their ability to efficiently intercalate and deintercalate ions, as well as their ion storage capacity. These characteristics depend not only on the material’s specific surface area but also on the inherent electrical conductivity of the active redox component and the conductive additives that provide electrons to balance the intercalating ions. This discussion will explore material design strategies aimed at improving the efficiency and sustainability of the DWE process, emphasizing methods to position DWE as a leading approach for water splitting.

References

[1] M. Iesalnieks, M. Vanags, L.L. Alsiņa, R. Eglītis, L. Grīnberga, P.C. Sherrell, A. Šutka, Adv. Sci., 11, 2024, 2401261. 

[2] M. Iesalnieks, M. Vanags, L.L. Alsiņa, A. Šutka, Increasing the capacity of pseudocapacitive WO3 auxiliary electrode for enhanced two-step decoupled acid water electrolysis, Renewable Energy, 228, 2024, 120599.

[3] M. Vanags, G. Kulikovskis, J. Kostjukovs, L. Jekabsons, A. Sarakovskis, K. Smits, L. Bikse, A. Sutka, Membrane-less amphoteric decoupled water electrolysis using WO3 and Ni(OH)2 auxiliary electrodes, Energy Environ. Sci., 15, 2022, 2021-2028.