Nano-Scale Engineering of Heterojunction for Alkaline Water Electrolysis

Chen, Yao; Xu, Zhenbo; Chen, George Zheng

Abstract

Alkaline water electrolysis is promising for low-cost and scalable hydrogen production. Renewable energy-driven alkaline water electrolysis requires highly effective electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). However, the most active electrocatalysts show orders of magnitude lower performance in alkaline electrolytes than that in acidic ones. To improve such catalysts, heterojunction engineering has been exploited as the most efficient strategy to overcome the activity limitations of the single component in the catalyst. In this review, the basic knowledge of alkaline water electrolysis and the catalytic mechanisms of heterojunctions are introduced. In the HER mechanisms, the ensemble effect emphasizes the multi-sites of different components to accelerate the various intermedium reactions, while the electronic effect refers to the d-band center theory associated with the adsorption and desorption energies of the intermediate products and catalyst. For the OER with multi-electron transfer, a scaling relation was established: the free energy difference between HOO* and HO* is 3.2 eV, which can be overcome by electrocatalysts with heterojunctions. The development of electrocatalysts with heterojunctions are summarized. Typically, Ni(OH)2/Pt, Ni/NiN3 and MoP/MoS2 are HER electrocatalysts, while Ir/Co(OH)2, NiFe(OH)x/FeS and Co9S8/Ni3S2 are OER ones. Last but not the least, the trend of future research is discussed, from an industry perspective, in terms of decreasing the number of noble metals, achieving more stable heterojunctions for longer service, adopting new craft technologies such as 3D printing and exploring revolutionary alternate alkaline water electrolysis.

Citation

Chen, Y., Xu, Z., & Chen, G. Z. (2024). Nano-Scale Engineering of Heterojunction for Alkaline Water Electrolysis. Materials, 17(1), Article 199. https://doi.org/10.3390/ma17010199

• Journal Article Type: Review
• Acceptance Date: Dec 27, 2023
• Online Publication Date: Dec 29, 2023
• Publication Date: Jan 1, 2024
• Deposit Date: Dec 30, 2023
• Publicly Available Date: Jan 2, 2024
• Journal: Materials
• Electronic ISSN: 1996-1944
• Publisher: MDPI
• Peer Reviewed: Peer Reviewed
• Volume: 17
• Issue: 1
• Article Number: 199
• DOI: https://doi.org/10.3390/ma17010199
• Keywords: Heterojunction; alkaline water electrolysis; HER; OER; d-band center; scaling relation
• Public URL: https://nottingham-repository.worktribe.com/output/29001395
• Publisher URL: https://www.mdpi.com/1996-1944/17/1/199
• Additional Information: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).