Unraveling the Most Relevant Features for the Design of Iridium Mixed Oxides with High Activity and Durability for the Oxygen Evolution Reaction in Acidic Media

Abstract

Proton exchange membrane water electrolysis (PEMWE) is the technology of choice for the large-scale production of green hydrogen from renewable energy. Current PEMWEs utilize large amounts of critical raw materials such as iridium and platinum in the anode and cathode electrodes, respectively. In addition to its high cost, the use of Ir-based catalysts may represent a critical bottleneck for the large-scale production of PEM electrolyzers since iridium is a very expensive, scarce, and ill-distributed element. Replacing iridium from PEM anodes is a challenging matter since Ir-oxides are the only materials with sufficient stability under the highly oxidant environment of the anode reaction. One of the current strategies aiming to reduce Ir content is the design of advanced Ir-mixed oxides, in which the introduction of cations in different crystallographic sites can help to engineer the Ir active sites with certain characteristics, that is, environment, coordination, distances, oxidation state, etc. This strategy comes with its own problems, since most mixed oxides lack stability during the OER in acidic electrolyte, suffering severe structural reconstruction, which may lead to surfaces with catalytic activity and durability different from that of the original mixed oxide. Only after understanding such a reconstruction process would it be possible to design durable and stable Ir-based catalysts for the OER. In this Perspective, we highlight the most successful strategies to design Ir mixed oxides for the OER in acidic electrolyte and discuss the most promising lines of evolution in the field.

New PVP–Ag or Pd-Doped Perovskite Oxide Hybrid Structures for Water Splitting Electrocatalysis

“…In order to make water splitting viable for large-scale H 2 production the electrocatalysts must also be stable and low cost [14]. Currently, Pt-based catalysts for the HER and Ru-and Ir-based catalysts for the OER are benchmarks when it comes to the performance evaluation of the other catalysts reported in the literature [15][16][17]. However, their scarcity and high cost are significant obstacles for large-scale applications, making the identification of non-noble materials that are both highly efficient and stable a main concern.…”

Theoretical Prediction and Experimental Verification of IrOx Supported on Titanium Nitride for Acidic Oxygen Evolution Reaction

“…Activity, stability, and material cost are three critical factors when designing acid oxygen evolution reaction (OER) electrocatalysts for practical applications. − To date, iridium oxide (IrO x )-based materials are the best acidic OER electrocatalysts that can meet the stability requirement under harsh operating conditions. − However, high costs and scarcity of Ir limit large-scale applications of IrO x . ,− Therefore, it is imperative to discover OER electrocatalysts with reduced Ir loading while maintaining their catalytic activity and stability in the acid environment.…”

New Hybrid Organic-Inorganic Structures for Water Splitting Electrocatalysts

“…In order to make water splitting viable for large-scale H2 production the electrocatalysts must also be stable and low cost [14]. Currently, Pt-based catalysts for the HER and Ru-and Ir-based catalysts for the OER are benchmarks when it comes to the performance evaluation of the other catalysts reported in the literature [15][16][17]. However, their scarcity and high cost are significant obstacles for large-scale applications, making the identification of non-noble materials that are both highly efficient and stable a main concern.…”