Tailored Electronic Structure of Ir in High Entropy Alloy for Highly Active and Durable Bifunctional Electrocatalyst for Water Splitting under an Acidic Environment

Jiseok Kwon; Seho Sun; Seunggun Choi; Kangchun Lee; Seonghan Jo; Keemin Park; Young Kwang Kim; Ho Bum Park; Hee Young Park; Jong Hyun Jang; Hyuksu Han; Ungyu Paik; Taeseup Song

doi:10.1002/adma.202300091

Tailored Electronic Structure of Ir in High Entropy Alloy for Highly Active and Durable Bifunctional Electrocatalyst for Water Splitting under an Acidic Environment

Adv Mater. 2023 Jun;35(26):e2300091. doi: 10.1002/adma.202300091. Epub 2023 May 11.

Authors

Jiseok Kwon¹, Seho Sun¹, Seunggun Choi¹, Kangchun Lee², Seonghan Jo¹, Keemin Park¹, Young Kwang Kim³, Ho Bum Park¹, Hee Young Park⁴, Jong Hyun Jang^{4

5}, Hyuksu Han⁶, Ungyu Paik¹, Taeseup Song¹

Affiliations

¹ Department of Energy Engineering, Hanyang University, 04763, Seoul, South Korea.
² Department of Electronic Engineering, Kyonggi University, 154-42 Gwanggyosan-ro, Suwon, Gyeonggi-do, 16227, South Korea.
³ Virtual Lab Inc, 49 Achasanro, Seoul, 04799, South Korea.
⁴ Center for Hydrogen Fuel Cell Research, Korea Institute of Science and Technology (KIST), Seoul, 02792, South Korea.
⁵ Energy & Environment Technology, KIST School, University of Science and Technology (UST), 02792, Seoul, South Korea.
⁶ Department of Energy Engineering, Konkuk University, 120 Neungdongro, Seoul, 05029, South Korea.

PMID: 36967600
DOI: 10.1002/adma.202300091

Abstract

Proton-exchange-membrane water electrolysis (PEMWE) requires an efficient and durable bifunctional electrocatalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, Ir-based electrocatalyst is designed using the high entropy alloy (HEA) platform of ZnNiCoIrX with two elements (X: Fe and Mn). A facile dealloying in the vacuum system enables the construction of a nanoporous structure with high crystallinity using Zn as a sacrificial element. Especially, Mn incorporation into HEAs tailors the electronic structure of the Ir site, resulting in the d-band center being far away from the Fermi level. Downshifting of the d-band center weakens the adsorption energy with reaction intermediates, which is beneficial for catalytic reactions. Despite low Ir content, ZnNiCoIrMn delivers only 50 mV overpotential for HER at -50 mA cm^-2 and 237 mV overpotential for the OER at 10 mA cm^-2 . Furthermore, ZnNiCoIrMn shows almost constant voltage for the HER and OER for 100 h and a high stability number of 3.4 × 10⁵ n_hydrogen n_Ir ^-1 and 2.4 × 10⁵ n_oxygen n_Ir ^-1 , demonstrating the exceptional durability of the HEA platform. The compositional engineering of ZnNiCoIrMn limits the diffusion of elements by high entropy effects and simultaneously tailors the electronic structure of active Ir sites, resulting in the modified cohesive and adsorption energies, all of which can suppress the dissolution of elements.

Keywords: PEM electrolysis; bifunctional electrocatalysts; compositional engineering; high entropy alloys.

Abstract

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