Reversible Ir-based multifunctional electrocatalyst for durable water splitting and fuel cell systems

Abstract

The voltage reversal of water electrolyzers and fuel cells induces a large positive potential on the hydrogen electrodes, followed by severe system degradation. Applying a reversible multifunctional electrocatalyst to the hydrogen electrode is a practical solution. Ir exhibits excellent catalytic reactivity for hydrogen evolution reactions (HER), and hydrogen oxidation reactions (HOR) around 0 V/RHE, yet irreversibly converts to amorphous IrOx at potentials > 0.8 V/RHE, which is an excellent catalyst for oxygen evolution reactions (OER), yet a poor HER and HOR catalyst. Harnessing these multifunctional catalytic characteristics, we designed a unique Ir-based electrocatalyst for OER, HER, and HOR. Under OER operation, the crystalline nanoparticle catalyst generates an atomically-thin, highly active IrOx layer, which reversibly transforms into a metallic Ir surface at more cathodic electrode potentials, restoring high catalytic activity for HER and HOR. Our analysis reveals that a metallic Ir subsurface to the thin IrOx surface layer can act as a catalytic substrate for the reduction of the dissolved Ir ion, creating reversibility. Our work not only uncovers new fundamental, uniquely reversible catalytic properties of nanoparticle catalysts, but also offers a practical materials-based solution to catalyst layer degradation of electrochemical energy conversion devices.

Surface self-reconstruction of telluride induced by in-situ cathodic electrochemical activation for enhanced water oxidation performance

“…The oxygen evolution reaction (OER) has hindered the efficiency of important electrochemical energy conversion processes, including H2 generation via water splitting, N2 fixation and CO2 reduction, on account of the sluggish kinetics [1][2][3][4].…”