Molecule Confined Isolated Metal Sites Enable the Electrocatalytic Synthesis of Hydrogen Peroxide

Abstract

levels of waste chemicals. [3] Thus, developing green and cost-effective techniques for the direct synthesis of H 2 O 2 is an ongoing challenge.Being green and sustainable, electrochemical synthesis powered by renewable electricity is an attractive route for direct on-site production of H 2 O 2 . In this process, oxygen is catalytically reduced to H 2 O 2 through the two-electron (2e -) oxygen reduction reaction (ORR). [4] For efficient H 2 O 2 production, electrocatalysts with high activity and selectivity are required. However, the catalytic performance of electrocatalysts is limited by the competitive four-electron (4e -) ORR pathway. To boost the desired performance toward 2e -ORR pathway, ideal electrocatalysts possess an optimal binding strength for OOH* such that OOH* desorption is favored versus further dissociation. [5] Therefore, one approach to engineer electrocatalysts for H 2 O 2 synthesis focuses on modulating the adsorption strength of OOH* such that subsequent dissociation is limited.In recent years, single-atom catalysts with isolated and welldefined metal sites have evolved into an important class of catalysts because of their high activity and selectivity in several chemical reactions. [6] In particular, isolated metals coordinated with nitrogen (denoted as MN x sites) in carbon-based materials have emerged as high performing electrocatalysts for reactions like oxygen reduction and CO 2 reduction. [7] MN x sites which catalyze oxygen reduction usually possess strong adsorption strengths of OOH* and a decreased kinetic barrier for OOH* dissociation. [8] These characteristics not only reduce the overpotential for ORR but also decrease the selectivity for the 2e -ORR pathway. [9] Being highly tunable, modulating the local structure and composition around the metal site can create active site motifs which preferentially desorb OOH* as H 2 O 2 instead of further OOH* dissociation. [10] This tunability provides a potential approach to modulate the OOH* behavior on single-atom catalysts toward the efficient H 2 O 2 generation.Herein, we present a molecular confinement strategy to enhance the selectivity of NiN x sites for the electrocatalytic production of H 2 O 2 . The aminoanthraquinone molecule (AQNH 2 ) is confined on carbon-supported NiN x sites (NiN x /C) through π-π interactions, creating a nanochannel between the molecule and NiN x . These confined NiN x active sites increase the selectivity to H 2 O 2 through the 2e -ORR process from below 55% to above 80%. The AQNH 2 confined NiN x active site achieves a high onset potential of 0.81 V at a current density The direct synthesis of hydrogen peroxide (H 2 O 2 ) through the two-electron oxygen reduction reaction is a promising alternative to the industrial anthraquinone oxidation process. Selectivity to H 2 O 2 is however limited by the four-electron pathway during oxygen reduction. Herein, it is reported that aminoanthraquinone confined isolated metal sites on carbon supports selectively steer oxygen reduction to H 2 O 2 through the two-el...

High‐Efficiency Electrosynthesis of Hydrogen Peroxide from Oxygen Reduction Enabled by a Tungsten Single Atom Catalyst with Unique Terdentate N1O2 Coordination

“…In conclusion, by combining the aforementioned XRD, STEM, XPS and XAS analysis, it is confirmed that the isolated W atoms with unique coordination structure of W 1 N 1 O 2 exist in W 1 /NO-C, rather than W nanoparticles/nanoclusters. It should be mentioned that, compared with traditional Fe, Co, Ni-based SACs with N coordination reported so far, [36,46,47,48] the as-obtained W 1 /NO-C features single-atom W metal center and unsaturated terdentate N 1 O 2 coordination environment. Such distinctive structures of W 1 / NO-C presumably contribute to distinct reaction selectivity and high-efficiency H 2 O 2 production, as will be discussed below.…”

Synergistic effect of doped nitrogen and oxygen-containing functional groups on electrochemical synthesis of hydrogen peroxide

“…Nowadays, some of the state-of-the-art catalysts for the electrocatalytic production of H 2 O 2 are precious-metal-based and alloy materials ( e.g. , Pd-based, 10–12 Pt-based, 13 and Pd–Au 14,15 ), single-atom catalysts, 16–18 and carbon-based materials. 19,20 These catalysts exhibit high activity and selectivity in a wide voltage range.…”

Highly Catalytic Selectivity for Hydrogen Peroxide Generation from Oxygen Reduction on Nd-Doped Bi4Ti3O12Nanosheets

“…Of course, both reaction products are extremely useful, especially when they can occur exclusively. Because the ORR occurs on the surface of used catalyst, the selectivity of the reaction is closely related to the type and surface properties of the catalyst. − The selectivity toward H 2 O 2 can be enhanced via careful catalyst design and fabrication. So it is a significant challenge and demand to develop electrocatalysts with high activity and selectivity in the selective formation of H 2 O 2 on account of the sluggish kinetics of ORR and the existence of competing 4e –1 ORR.…”