| 초록 |
The voltage reversal of water electrolyzers and fuel cells induces a large positive potential on the hydrogen electrodes, after which severe system degradation ensues. Applying a reversible multifunctional electrocatalyst to the hydrogen electrode is a promising solution. Ir exhibits excellent catalytic reactivity for hydrogen evolution reaction (HER), and hydrogen oxidation reaction (HOR) around 0 V/RHE, yet irreversibly converts to amorphous IrOx at potentials ＞ 0.8 V/RHE, which is an excellent catalyst oxygen evolution reaction (OER), yet a poor HER and HOR catalyst. We designed a reversible Ir-based multifunctional electrocatalyst with high crystallinity for OER, HER, and HOR. Our results revealed that highly crystalline nanoparticles form a thin IrOx layer during OER, which reversibly converts to a metallic surface under negative potential, restoring catalytic activity for HER and HOR. Metallic Ir subsurface to the thin IrOx surface layer can be catalytic substrate for the reduction of the dissolved Ir ion, creating reversibility. Our work illustrates unique reversible properties of nanoparticles by altering crystallinity and provides new insights into nano-catalyst design. |
