Promoting Oxygen Evolution Reaction Induced by Synergetic Geometric and Electronic Effects of IrCo Thin-Film Electrocatalysts

Abstract

The advancement of water electrolysis technology has seemingly plateaued. Further advances require new strategies to address the key limitations of the oxygen evolution reaction: high overpotential and low stability of electrode materials. Herein, we designed a nanoporous Ir3Co-core@IrO2-shell electrocatalyst with 5 and 3 times higher mass activity and 6 and 2 times higher activity–stability factors than conventional IrO2 nanoparticles and Ir nanoporous electrocatalysts, respectively. The origin of the performance enhancement in the Ir3Co-core@IrO2-shell electrocatalyst was revealed in computational density functional theory calculations. The residual Co after the dealloying process resulted in a down-shift of the d-band center position, thus weakening the −OH* adsorption energy. In addition, the electronic conductivity was enhanced by the three-dimensionally interconnected structure. Under high-current-density operating conditions, the Ohmic losses were reduced by the ultrafast charge transfer pathway provided by the metallic IrCo core.

NiFe Alloy Integrated with Amorphous/Crystalline NiFe Oxide as an Electrocatalyst for Alkaline Hydrogen and Oxygen Evolution Reactions

“…Water electrolyzers show great promise for solving this problem by converting the surplus renewable energy power into chemical energy stored in H 2 chemical bonds. 1 − 4 The H 2 can be used in fuel cells to produce electricity to power electric vehicles and residential systems. Water electrolysis for H 2 production has been conducted under both acidic or alkaline conditions.…”

“…However, reliable energy storage systems are required to compensate for the intermittent nature of energy generation from renewable energy sources, such as solar and wind power. Water electrolyzers show great promise for solving this problem by converting the surplus renewable energy power into chemical energy stored in H 2 chemical bonds. − The H 2 can be used in fuel cells to produce electricity to power electric vehicles and residential systems. Water electrolysis for H 2 production has been conducted under both acidic or alkaline conditions.…”

IrCo Nanoparticles Encapsulated with Carbon Nanotubes for Efficient and Stable Acidic Water Splitting

“…Electrocatalytic water splitting technology can convert unstable solar and wind energy into clean and storable hydrogen energy, which currently accounts for about 4% of global hydrogen production. − Further advancements in this technology are expected to alleviate the energy crisis facing the world today. − The total water splitting consists of two half–cell reactions, the hydrogen evolution reaction (HER) at cathode and the oxygen evolution reaction (OER) at anode. − Recent breakthroughs in polymer exchange membrane (PEM) technology have accelerated water splitting under acidic conditions as compared to conventional alkaline water splitting. , PEM-based acidic electrolyzers have multiple advantages such as easy separation of gas production, low cost, few by-products, and high proton conductivity. − In an acidic solution, the high proton concentration provides a kinetic advantage to the HER process, allowing it to reach a large current at a low overpotential. , However, the OER process is an inert four-electron process, which usually requires a high overpotential to drive the electrocatalyst to work. , Unfortunately, the harsh acidic environment under a high overpotential can cause the rapid dissolution of metal-based active centers, leading to grievous catalyst deactivation. , Up to now, various advanced Ir-based electrocatalysts have been constructed and used for efficient acidic OER. − Nevertheless, during the long-term OER process, the oxidation states of Ir-based species change strongly, and even stable IrO x would be gradually dissolved and inactivated in an acidic medium. , Therefore, it is crucial to design and develop highly active and stable bifunctional electrocatalysts in acidic media to promote water electrolysis technology. , …”

“…25−27 Nevertheless, during the long-term OER process, the oxidation states of Ir-based species change strongly, and even stable IrO x would be gradually dissolved and inactivated in an acidic medium. 23,28 Therefore, it is crucial to design and develop highly active and stable bifunctional electrocatalysts in acidic media to promote water electrolysis technology. 29,30 To enhance catalyst activity and reduce the amount of noble metals, researchers have incorporated non-noble metals such as Fe, Co, Ni, and Cu into Ir to form Ir-based alloys or other hybrids.…”

Deteriorated Balance between Activity and Stability via Ru Incorporation into Ir-Based Oxygen Evolution Nanostructures

“…1,2 However, there are persistent challenges related to material limitations in acidic environments, the high kinetics barrier associated with 4-electron transfer, and the inherent instability during the oxygen evolution reaction (OER). 3,4 To address these challenges, researchers have focused on the development of electrocatalysts based on iridium, which exhibits high electrochemical stability, or ruthenium, which possess high intrinsic activity. These advancements have been achieved through methodologies such as alloy formation and increasing the active surface area.…”