Bifunctional Electrode Design Targeting Co‐Enhanced Kinetics and Mass Transport for Hydrogen and Water Oxidation Reactions

• Published in: Advanced functional materials 2023-10, Vol.33 (40), p.n/a
• Main Authors: Kim, Ye Ji, Lim, Ahyoun, Lee, Gyu Rac, Kim, Minjoon, Kim, Jin Young, Kim, Jong Min, Jung, Yeon Sik, Park, Hyun S.
• Format: Article
• Language: English
• Subjects: 3D nanostructure engineering; Catalysis; Catalysts; Electrodes; Electrolytic cells; Energy conversion; hydrogen oxidation reaction; Iridium; Mass transport; Materials science; Nanowires; Noble metals; Oxidation; oxygen evolution reaction; Oxygen evolution reactions; polymer electrolyte membrane unitized regenerative fuel cells; Proton exchange membrane fuel cells; Regenerative fuel cells
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202302586

Bifunctional catalysts based on noble metals have achieved practical‐level performances in round‐trip energy conversion systems. However, the required amount of noble metals should be substantially reduced via a new catalyst design that can pursue the synergy of the constituent materials’ intrinsic properties and architectural maneuver over reactant/product transport. In this study, cross‐stacked Ir and Pt nanowires resolved the bottlenecks of two reactions essential for the hydrogen‐based energy system: i) hydrogen spillover phenomenon between Pt and Ir nanowires to expedite the hydrogen oxidation reaction and ii) spacing Ir nanowires sufficiently to enhance the mass transport of the oxygen evolution reaction. Simultaneously accommodating the different strategies within the single catalyst layer, a new horizon to design a bifunctional electrode is proposed with the high performance of polymer electrolyte membrane unitized regenerative fuel cells: 47% of round‐trip efficiency at 0.5 A cm−2 with total noble metal loading < 0.3 mg cm−2. A multiscale woodpile (MsWP) structure of Ir‐Pt bifunctional electrode is suggested to enhance kinetics based on hydrogen spillover and efficient mass transport for improved hydrogen and water oxidation reactions. Beyond the proof of concept in ideal experimental conditions, the MsWP anode electrode in a unitized regenerative fuel cell demonstrated practical performance with noble metal loading smaller than 0.3 mg cm–2.