Accelerating Alkaline Water Electrolysis by Integrating Solar-Thermal Energy and Temperature-Sensitive Ni-Co-Fe Layered Double Hydroxide Catalysts

Abstract

Among various electrolysis technologies, alkaline water electrolysis (AWE) is considered the most mature for industrial scale-up and has robust cost-effectiveness. However, AWE’s cold-start nature requires a ramp-up time (ca. 1 hour). This makes it challenging to integrate with renewable energy sources, which are difficult to predict. Water electrolysis exhibits a pronounced temperature dependence, with overpotential decreasing [1, 2], and some research groups have demonstrated AWEs with external heat sources [1, 3]. Our intended solution is to introduce a chemically resistant solar thermal collector that provides a heated electrolyte to increase reactivity and reduce ramp-up time, and to develop oxygen evolution reaction (OER) catalysts with high-temperature sensitivity. In this work, we discuss key dimensional design aspects of the thermal collector for an alkaline electrolyser and present the performance of transition-metal oxide catalysts (Ni-Co-Fe LDH on Ni plate) for OER under low-grade solar thermal energy (below 80°C). The results show a reduction in overpotential with increasing temperature, with the highest overpotential reduction rate of over 4.6 mV/°C, and our DFT study also supports the observed change in kinetics at elevated temperatures. This study offers an alternative solution to reduce the required electric energy during the ramp-up period by leveraging the benefits of both thermal energy and optimised electrode materials to increase AWE's cost-effectiveness and competitiveness. [1] B. Zhang, Q. Daniel, M. Cheng, L. Fan and L. Sun, Faraday Discuss, 2017, 198, 169–179. [2] A. S. Salunke, R. J. Deokate, S. T. Salunke, S. H. Mujawar, N. K. Shrestha, H. Im and A. I. Inamdar, J Alloys Compd, 2024, 989, 174334. [3] G. Shi, T. Tano, D. A. Tryk, M. Yamaguchi, A. Iiyama, M. Uchida, K. Iida, C. Arata, S. Watanabe and K. Kakinuma, ACS Catal, 2022, 12, 14209–14219.