Ultrafine-Grained Porous Ir-Based Catalysts for High-Performance Overall Water Splitting in Acidic Media

Abstract

Iridium (Ir)-based materials are known to be state-of-the-art electrocatalysts for catalyzing the oxygen evolution reaction (OER) in proton-exchange membrane (PEM) water electrolysis. However, it remains challenging for Ir-based catalysts to simultaneously achieve high catalytic activity and good stability in a strongly acidic environment. Herein, we report the fabrication of self-supported nanoporous ultrafine-grained IrO 2 electrodes (np-IrO 2 ) through the electrochemical activation of melt-spun Ir 12 Al 88 ribbons under the OER conditions in 0.5 M H 2 SO 4 . The as-obtained np-IrO 2 needs only 240 mV to deliver 10 mA cm −2 and can sustain continuous OER electrolysis in strong acid at an unusually high current density of 100 mA cm −2 for 30 h without substantial degradation. Moreover, we find that the electrochemical activation of Ir 12 Al 88 ribbons under the hydrogen evolution reaction (HER) conditions results in the formation of nanoporous IrAl alloy electrodes (np-IrAl), which show outstanding catalytic performance for HER in 0.5 M H 2 SO 4 . We further demonstrate that by using np-IrO 2 as an anode and np-IrAl as a cathode, we can accomplish overall acidic water splitting at 10 mA cm −2 with a low voltage of 1.52 V. Remarkably, the np-IrO 2 ∥np-IrAl electrode pair is able to split water stably in 0.5 M H 2 SO 4 at a high current density of 100 mA cm −2 for up to 40 h, showing substantial promise for use in PEM water electrolysis.

Accelerating Bubble Detachment in Porous Transport Layers with Patterned Through-Pores

“…However, mass transport losses must first be minimized in order to facilitate high current density operation. While extensive research has been conducted for designing the catalyst layer − and membrane to advance electrolyzer performance, the strategic design of porous transport layers (PTLs) for high current density operation ( i > 5 A/cm 2 ) has been largely overlooked in the field.…”

In Situ Kinetic Observations on Crystal Nucleation and Growth

“…Element- and alloy-based metal nanomaterials, showing unique opto-electronic, magnetic, thermal, and catalytic properties, have been widely used in many fields, such as lithium/sodium batteries, − fuel cells, − catalysis, − biomedicine, − solar cells, − and data storage. − The properties of nanomaterials depend on their size and morphology, which can be regulated by the crystal nucleation and growth mechanisms. ,,, Hence, the study of nucleation and growth dynamics on these critical nanomaterials have intensified over the past decades . Recently, accompanied with the development of new in situ observation technologies and the improvement of time and spatial resolutions in all kinds of microscopes, the in situ dynamic observations on crystal nucleation and growth of different dimensional nanomaterials including zero-dimensional (0D) NPs, one-dimensional (1D) NRs/NWs, and two-dimensional nanostructures have been achieved at the nanoscale and even at the atomic scale.…”

Strategies for Electrochemically Sustainable H2 Production in Acid

“…Among them, Ir‐Co materials [ 134 , 135 , 136 ] have received more research interest. However, Ir‐Ni [ 137 ] and Ir‐Al catalysts, [ 138 ] show more potential for application in symmetrical electrode systems. The types of active metal components and the substrates are two key factors to be considered in designing interconvertible anodes and cathodes: 1) To achieve bi‐functional activity, a general approach is to integrate different active metals.…”