Metal-Compound-Based Electrocatalysts for Hydrogen Peroxide Electrosynthesis and the Electro-Fenton Process

Abstract

Hydrogen peroxide (H 2 O 2 ) is a powerful oxidant with many applications, but its chemical production is unsustainable and unsafe. Decentralized electrosynthesis of H 2 O 2 via the selective two-electron oxygen reduction reaction (2e − ORR) is attractive, which demands active, selective, stable, and cost-effective electrocatalysts in acidic and neutral solutions where H 2 O 2 is stable. Metal compounds are an emerging class of 2e − ORR catalysts with diverse and tunable structural motifs for optimizing H 2 O 2 electrosynthesis, yet they remain underexplored, with poorly understood structure−property relationships. This Focus Review summarizes the recent computational and experimental developments in metal-compound-based acidic and neutral 2e − ORR catalysts, and the resultant mechanistic understanding and catalyst design rules for guiding future catalyst discoveries. The many fundamental and practical factors at the reaction, catalyst, electrode, and device levels that impact H 2 O 2 electrosynthesis are systematically discussed. Metal-compound-based acidic 2e − ORR catalysts can also enable efficient electro-Fenton processes for environmental remediation and biomass valorization.

Defect engineering of two-dimensional materials for advanced energy conversion and storage

“…[294][295][296][297] The other is a twostep 2e À transfer route involving the generation of H 2 O 2 (under acidic conditions) or HO 2 À (under alkaline conditions) as the intermediates, which is often used for industrial H 2 O 2 production. [298][299][300][301] Specifically, for the direct 4e À pathway, there are two possible mechanisms with different intermediates involved (associative: O*, OOH*, and OH*; dissociative: O* and OH*) depending on the original O 2 dissociation energy barrier. In general, the ORR activity is governed by both the thermodynamic adsorption energetics of these intermediates and the kinetic energy barriers between different reaction steps.…”

High-entropy alloys in electrocatalysis: from fundamentals to applications

“…The indirect mechanism involves a 2e pathway for H 2 O 2 formation and another 2e pathway for water formation. 282,283 The 2e pathway is conducive to H 2 O 2 production. In the ORR process, multiple intermediates are involved, including the reduction and decomposition of O 2 *, as well as the removal of adsorbed O*, HO*, and H 2 O*.…”

Oxygen-Reduction-Triggered Cathodic Electrodeposition of Mn-Based Metal–Organic Framework Nanoflakes as Oxygen Evolution Electrocatalysts

“…The oxygen reduction reaction (ORR) is an important reaction that can find applications in a variety of fields. The 4-electron (4-e) ORR to H 2 O or OH – are usually used as the cathodic reaction of fuel cell in the energy field. − However, it is a green strategy to synthesize multipurpose H 2 O 2 through a 2-electron (2-e) ORR. − Moreover, the 2-e ORR has been applied in the electro-Fenton process to deal with organic pollutants. , Recently, it was reported that the ORR could be applied to assist the electrochemical synthesis of metal–organic frameworks (MOFs) on the electrode in the nonaqueous electrolyte. , …”

“…4−6 Moreover, the 2-e ORR has been applied in the electro-Fenton process to deal with organic pollutants. 7,8 Recently, it was reported that the ORR could be applied to assist the electrochemical synthesis of metal−organic frameworks (MOFs) on the electrode in the nonaqueous electrolyte. 9,10 MOFs are a new class of porous materials that are formed via the coordination between metal ions and organic ligands.…”