H2O2 Selectivity Research Articles

Tuning proton affinity on Co-N-C atomic interface to disentangle activity-selectivity trade-off in acidic oxygen reduction to H2O2.

In oxygen reduction reaction to H2O2via two-electron pathway (2e- ORR), adsorption strength of oxygen-containing intermediates determines both catalytic activity and selectivity. However, it also causes activity-selectivity trade-off. Herein, we propose a novel strategy through modulating the interaction between protons and *OOH intermediates to break the activity-selectivity trade-off for highly active and selective 2e- ORR. Taking the typical cobalt-nitrogen-carbon single-atom catalyst as an example, boron heteroatoms doped into second coordination sphere of CoN4 (Co1-NBC) increase proton affinity on catalyst surface, facilitating proton attack on the former oxygen of *OOH and thereby promoting H2O2 formation. As a result, Co1-NBC simultaneously achieves prominent 2e- ORR activity and selectivity in acid with onset potential of 0.724 V vs. RHE and H2O2 selectivity of 94%, surpassing most reported catalysts. Furthermore, Co1-NBC exhibits a record-high H2O2 productivity of 202.7 mg cm-2 h-1 and a remarkable stability of 60 h at 200 mA cm-2 in flow cell. This work provides new insights into resolving activity-selectivity trade-off in electrocatalysis.

Tuning proton affinity on Co–N–C atomic interface to disentangle activity‐selectivity trade‐off in acidic oxygen reduction to H2O2

In oxygen reduction reaction to H2O2via two‐electron pathway (2e‐ ORR), adsorption strength of oxygen‐containing intermediates determines both catalytic activity and selectivity. However, it also causes activity‐selectivity trade‐off. Herein, we propose a novel strategy through modulating the interaction between protons and *OOH intermediates to break the activity‐selectivity trade‐off for highly active and selective 2e‐ ORR. Taking the typical cobalt‐nitrogen‐carbon single‐atom catalyst as an example, boron heteroatoms doped into second coordination sphere of CoN4 (Co1‐NBC) increase proton affinity on catalyst surface, facilitating proton attack on the former oxygen of *OOH and thereby promoting H2O2 formation. As a result, Co1‐NBC simultaneously achieves prominent 2e‐ ORR activity and selectivity in acid with onset potential of 0.724 V vs. RHE and H2O2 selectivity of 94%, surpassing most reported catalysts. Furthermore, Co1‐NBC exhibits a record‐high H2O2 productivity of 202.7 mg cm‐2 h‐1 and a remarkable stability of 60 h at 200 mA cm‐2 in flow cell. This work provides new insights into resolving activity‐selectivity trade‐off in electrocatalysis.

Accelerated Proton‐Coupled Electron Transfer via Engineering Palladium Sub‐Nanoclusters for Scalable Electrosynthesis of Hydrogen Peroxide

AbstractElectrosynthesis of H2O2 from oxygen reduction reaction via a two‐electron pathway is vital as an alternative for the energy‐intensive anthraquinone process. However, this process is largely hindered in neutral and alkaline conditions due to sluggish kinetics associated with the transformation of intermediate O2* into OOH* via proton‐coupled electron transfer sourced from slow water dissociation. Herein, we developed Pd sub‐nanoclusters on the nickel ditelluride nanosheets (Pd SNCs/NiTe2) to enhance the performance of H2O2 electrosynthesis. The newly‐developed Pd SNCs/NiTe2 exhibited a H2O2 selectivity of as high as 99 % and a positive shift of onset potential up to 0.81 V. Combined theoretical calculations and experimental studies (e.g., X‐ray absorption and attenuated total reflectance‐Fourier transform infrared spectra measurements) revealed that the Pd sub‐nanoclusters supported by NiTe2 nanosheets efficiently reduced the energy barrier of water dissociation to generate more protons, facilitating the proton feeding kinetics. When used in a flow cell, Pd SNCs/NiTe2 cathode efficiently produced H2O2 with a maximum yield rate of 1.75 mmol h−1 cm−2 and a current efficiency of 95 % at 100 mA cm−2. Further, an accumulated H2O2 concentration of 1.43 mol L−1 was reached after 10 hours of continuous electrolysis, showing the potential for practical H2O2 electrosynthesis.

Modulating Core Polarity in Metal-free Covalent Organic Frameworks for Selective Electrocatalytic Hydrogen Peroxide Production.

Tuning the charge density at the active site to balance the adsorption ability and reactivity of oxygen is extremely significant for driving a two-electron oxygen reduction reaction (ORR) to produce hydrogen peroxide (H2O2). Herein, we have highlighted the influence of intermolecular polarity in covalent organic frameworks (COFs) on the efficiency and selectivity of electrochemical H2O2 production. Different C3 symmetric building blocks have been utilized to regulate the charge density at the active sites. The benzene-cored COF, which exhibits reduced polarity than the triazine-cored COF, displayed enhanced performance in H2O2 production, achieving 93.1% selectivity for H₂O₂ at 0.4 V with almost two-electron transfer and a faradaic efficiency of 90.5%. In-situ electrochemical Raman spectroscopy and scanning electrochemical microscopy (SECM) were employed to confirm H₂O₂ generation and analyze spatial reactivity patterns. These techniques provided detailed insights into localized catalytic behavior, emphasizing the influence of core polarity.

Modulating Core Polarity in Metal‐free Covalent Organic Frameworks for Selective Electrocatalytic Hydrogen Peroxide Production

Tuning the charge density at the active site to balance the adsorption ability and reactivity of oxygen is extremely significant for driving a two‐electron oxygen reduction reaction (ORR) to produce hydrogen peroxide (H2O2). Herein, we have highlighted the influence of intermolecular polarity in covalent organic frameworks (COFs) on the efficiency and selectivity of electrochemical H2O2 production. Different C3 symmetric building blocks have been utilized to regulate the charge density at the active sites. The benzene‐cored COF, which exhibits reduced polarity than the triazine‐cored COF, displayed enhanced performance in H2O2 production, achieving 93.1% selectivity for H₂O₂ at 0.4 V with almost two‐electron transfer and a faradaic efficiency of 90.5%. In‐situ electrochemical Raman spectroscopy and scanning electrochemical microscopy (SECM) were employed to confirm H₂O₂ generation and analyze spatial reactivity patterns. These techniques provided detailed insights into localized catalytic behavior, emphasizing the influence of core polarity.

Metal-Based Oxygen Reduction Electrocatalysts for Efficient Hydrogen Peroxide Production.

Hydrogen peroxide (H2O2) is a high-value chemical widely used in electronics, textiles, paper bleaching, medical disinfection, and wastewater treatment. Traditional production methods, such as the anthraquinone oxidation process and direct synthesis, require high energy consumption, and involve risks from toxic substances and explosions. Researchers are now exploring photochemical, electrochemical, and photoelectrochemical synthesis methods to reduce energy use and pollution. This review focuses on the 2-electron oxygen reduction reaction (2e- ORR) for the electrochemical synthesis of H2O2, and discusses how catalyst active sites influence O2 adsorption. Strategies to enhance H2O2 selectivity by regulating these sites are presented. Catalysts require strong O2 adsorption to initiate reactions and weak *OOH adsorption to promote H2O2 formation. The review also covers advances in single-atom catalysts (SACs), multi-metal-based catalysts, and highlights non-noble metal oxides, especially perovskite oxides, for their versatile structures and potential in 2e- ORR. The potential of localized surface plasmon resonance (LSPR) effects to enhance catalyst performance is also discussed. In conclusion, emphasis is placed on optimizing catalyst structures through theoretical and experimental methods to achieve efficient and selective H2O2 production, aiming for sustainable and commercial applications.

Nature-inspired N, O Co-Coordinated Manganese Single-Atom Catalyst for Efficient Hydrogen Peroxide Electrosynthesis.

The two-electron oxygen reduction reaction (2e- ORR) is a pivotal pathway for the distributed production of hydrogen peroxide (H2O2). In nature, enzymes containing manganese (Mn) centers can convert reactive oxygen species into H2O2. However, Mn-based heterogeneous catalysts for 2e- ORR are scarcely reported. Herein, we developed a nature-inspired single-atom electrocatalyst comprising N, O co-coordinated Mn sites, utilizing carbon dots as the modulation platform (Mn CD/C). As-synthesized Mn CD/C exhibited exceptional 2e- ORR activity with an onset potential of 0.786 V and a maximum H2O2 selectivity of 95.8%. Impressively, Mn CD/C continuously produced 0.1 M H2O2 solution at 200 mA/cm2 for 50 h in the flow cell, with negligible loss in activity and H2O2 faradaic efficiency, demonstrating practical application potential. The enhanced activity was attributed to the incorporation of Mn atomic sites into the carbon dots. Theoretical calculations revealed that the N, O co-coordinated structure, combined with abundant oxygen-containing functional groups on the carbon dots, optimized the binding strength of intermediate *OOH at the Mn sites to the apex of the catalytic activity volcano. This work illustrates that carbon dots can serve as a versatile platform for modulating the microenvironment of single-atom catalysts and for the rational design of nature-inspired catalysts.

Selective O2-to-H2O2 Electrosynthesis by a High-Performance, Single-Pass Electrofiltration System Using Ibuprofen-Laden CNT Membranes.

Producing H2O2 through a selective, two-electron (2e) oxygen reduction reaction (ORR) is challenging, especially when it serves as an advanced oxidation process (AOP) for cost-effective water decontamination. Herein, we attain a 2e-selectivity H2O2 production using a carbon nanotube electrified membrane with ibuprofen (IBU) molecules laden (IBU@CNT-EM) in an ultrafast, single-pass electrofiltration process. The IBU@CNT-EM can generate H2O2 at a rate of 25.62 mol gCNT-1 h-1 L-1 in the permeate with a residence time of 1.81 s. We demonstrated that an interwoven, hydrophilic-hydrophobic membrane nanostructure offers an excellent air-to-water transport platform for ORR acceleration. The electron transfer number of the ORR for IBU@CNT at neutral pH was confirmed as 2.71, elucidating a near-2e selectivity to H2O2. Density functional theory (DFT) studies validated an exceptional charge distribution of the IBU@CNT for the O2 adsorption. The adsorption energies of the O2 and *OOH intermediates are proportional to the H2O2 selectivity (64.39%), higher than that of the CNT (37.81%). With the simple and durable production of H2O2 by IBU@CNT-EM electrofiltration, the permeate can actuate Fenton oxidation to efficiently decompose emerging pollutants and inactivate bacteria. Our study introduces a new paradigm for developing high-performance H2O2-production membranes for water treatment by reusing environmental functional materials.

In Situ Carbon Thermal Reduction to Enrich Sulfur-Vacancy in Nickel Disulfide Cathode for Efficient Synthesizing Hydrogen Peroxide.

Transition metal catalysts are widely used in the 2e- ORR due to their cost-effectiveness. However, they often encounter issues related to low activity. Defect engineering are used on developing highly active catalysts, which can effectively modify active sites and promote electron transfer. Here, carbon-coated Ni3S2 (Ni3S2@C), where the additional sulfur vacancies (VS) is prepared induced by the carbon layer is coupled with active nickel sites. Through in situ and ex situ experiments combined with DFT calculations, it is demonstrated that the carbon layer can regulate the quantity of VS in Ni3S2. Materials with a higher concentration of VS exhibit enhanced 2e- ORR activity and higher H2O2 selectivity. In situ Raman spectroscopy confirms that Ni serves as the key active site in this catalyst. DFT calculations indicate that the OOH binding energy (ΔG) decreases with an increase in the number of VS, favoring the protonation of *OOH to generate H2O2. Upon performance testing, the average H2O2 selectivity is 92.3%, with the highest yield reaching up to 3860mmolgcat-1h-1. It is noteworthy that Ni3S2@C exhibits high stability, with only a slight decrease in 2e- pathway selectivity after 5000 cycles of ADT.

Construction of One-Dimensional Covalent-Organic Framework Coordinated with Main Group Metals for Selective Electrochemical Synthesis of H2O2.

Covalent-organic frameworks (COFs) are promising electrocatalysts for the selective synthesis of H2O2 through the two-electron oxygen reduction reaction (2e- ORR). However, the design and synthesis of efficient and stable COF-based electrocatalysts is still challenging. In this work, a predesigned 1,10-phenanthroline-based one-dimensional COF (PYTA-PTDE-COF) was constructed to anchor main group metal (In, Sn, and Sb) as electrocatalysts toward 2e- ORR. The catalysts are featured with fully exposed metalated side chains. Structural characterization revealed that PYTA-PTDE-M's (M = In, Sn, and Sb) are all quite similar, except for the coordinated metal ions with the maintenance of good crystallinity. They all exhibited satisfying activity and selectivity toward 2e- ORR under alkaline conditions. Among them, PYTA-PTDE-Sb exhibited the best performance (Eonset is 0.765 V, the H2O2 selectivity is 96%, and the yield rate is 209.2 mmol gcat-1 h-1). Moreover, it also delivered superior stability with almost no attenuation of current density during the long-time test. Theoretical calculations revealed that the Sb metal site in the COFs has the lowest adsorption strength of *OOH, which could be the main reason for its superior selectivity. The PYTA-PTDE-Sb assembled zinc-air battery realizes not only the supply of clean energy but also the production of green chemicals, showing it is highly promising in practical applications. This work offers an example for designing main group metal-coordinated 1D COFs and reveals fundamental structure-activity relationship toward 2e- ORR.

A Computation-Guided Design of Highly Defined and Dense Bimetallic Active Sites on a Two-Dimensional Conductive Metal-Organic Framework for Efficient H2O2 Electrosynthesis.

Electrochemical synthesis of hydrogen peroxide (H2O2) via the two-electron oxygen reduction reaction (2e--ORR) provides an alternative method to the energy-intensive anthraquinone method. Metal macrocycles with precise coordination are widely used for 2e--ORR electrocatalysis, but they have to be commonly loaded on conductive substrates, thus exposing a large number of 2e--ORR-inactive sites that result in poor H2O2 production rate and efficiency. Herein, guided by first-principle predictions, a substrate-free and two-dimensional conductive metal-organic framework (Ni-TCPP(Co)), composed of CoN4 sites in porphine(Co) centers and Ni2O8 nodes, is designed as a multi-site catalyst for H2O2 electrosynthesis. The approperiate distance between the CoN4 and Ni2O8 sites in Ni-TCPP(Co) weakens the electron transfer between them, thus ensuring their inherent activities and creating high-density active sites. Meanwhile, the intrinsic electronic conductivity and porosity of Ni-TCPP(Co) further facilitate rapid reaction kinetics. Therefore, outstanding 2e--ORR electrocatalytic performance has been achieved in both alkaline and neutral electrolytes (>90 %/85 % H2O2 selectivity within 0-0.8 V vs. RHE and >18.2/18.0 mol g-1 h-1 H2O2 yield under alkaline/neutral conditions), with confirmed feasibility for water purification and disinfection applications. This strategy thus provides a new avenue for designing catalysts with precise coordination and high-density active sites, promoting high-efficiency electrosynthesis of H2O2 and beyond.

A Computation‐Guided Design of Highly Defined and Dense Bimetallic Active Sites on a Two‐Dimensional Conductive Metal–Organic Framework for Efficient H2O2 Electrosynthesis

AbstractElectrochemical synthesis of hydrogen peroxide (H2O2) via the two‐electron oxygen reduction reaction (2e−‐ORR) provides an alternative method to the energy‐intensive anthraquinone method. Metal macrocycles with precise coordination are widely used for 2e−‐ORR electrocatalysis, but they have to be commonly loaded on conductive substrates, thus exposing a large number of 2e−‐ORR‐inactive sites that result in poor H2O2 production rate and efficiency. Herein, guided by first‐principle predictions, a substrate‐free and two‐dimensional conductive metal–organic framework (Ni‐TCPP(Co)), composed of CoN4 sites in porphine(Co) centers and Ni2O8 nodes, is designed as a multi‐site catalyst for H2O2 electrosynthesis. The approperiate distance between the CoN4 and Ni2O8 sites in Ni‐TCPP(Co) weakens the electron transfer between them, thus ensuring their inherent activities and creating high‐density active sites. Meanwhile, the intrinsic electronic conductivity and porosity of Ni‐TCPP(Co) further facilitate rapid reaction kinetics. Therefore, outstanding 2e−‐ORR electrocatalytic performance has been achieved in both alkaline and neutral electrolytes (>90 %/85 % H2O2 selectivity within 0–0.8 V vs. RHE and >18.2/18.0 mol g−1 h−1 H2O2 yield under alkaline/neutral conditions), with confirmed feasibility for water purification and disinfection applications. This strategy thus provides a new avenue for designing catalysts with precise coordination and high‐density active sites, promoting high‐efficiency electrosynthesis of H2O2 and beyond.

Core-shell structured composite high-efficiency catalyst Co@Pd/TiO2 with a compressed-strain Pd shell for the direct synthesis of H2O2

Direct synthesis of H2O2 from H2 and O2 still faces the dilemma of low selectivity and productivity due to the O-O bond dissociation. To expedite the resolution of this issue, we introduce a core–shell structured catalyst Co@Pd/TiO2 with a compressed-strain Pd shell. The Co@Pd/TiO2 catalyst demonstrates a superior H2O2 productivity of 6.95 × 103 mmol·gPd-1·h−1 and H2O2 selectivity of 98.1 %, with enhancements of over 192 % and 139 %, respectively, when compared to Pd/TiO2. The construction of the compressed-strain Pd shell on the Co@Pd/TiO2 catalyst induces a winder width (wd) and a lower center (εd) of the Pd d-band, allowing the Co@Pd/TiO2 catalyst to achieve the following benefits for improving H2O2 selectivity and productivity: (1) Reducing the degree of electron back-donation to O2* (* denotes adsorbed state, the same below), thus inhibiting the cleavage of the O-O bond in O2*; (2) Showing a weaker Pd-O bond strength, which stabilizes the OOH* species and suppresses the breakage of the O-O bond therein; (3) Weakening the interaction between the catalyst and chemical substances, thereby restraining H2O2 degradation.

Highly efficient electrosynthesis of hydrogen peroxide through reversible transformation between catechol and o-benzoquinone on polydopamine modified carbon black

Carbon-based materials are more promising catalysts for H2O2 electrochemical production. However, the common method for modifying carbon-based materials is surface functionalization with harsh and uncontrollable reaction conditions, hindering the precise regulation of the active sites. Herein, we proposed a carbon-based material modified by polydopamine (CB-PDA) that was easily prepared and used in air diffusion electrode system for H2O2 production. The rapid and reversible transformation between catechol and o-benzoquinone on PDA could improve the H2O2 selectivity from 75.5 % to 97.0 % during the electrocatalytic process. The detection of adsorbed *HOOH and *OOH in oxygen reduction reaction proved the preference of CB-PDA for the two-electron pathway. The H2O2 formation rate constant of CB-PDA increased significantly from 25.85 to 60.82 mM h−1. The highest cumulative H2O2 concentration could reach 10200 mg L−1 in 9 h. Long-term operation tests proved the good operational stability. Furthermore, this system was cost-effective without additional aeration energy consumption and could achieve rapid disinfection in 10 min, which would have great potential to be used in environmental remediation.

Doped‐Sn Enhanced the Performance of BiOCl Nanosheet on Electrocatalytic Synthesis of Hydrogen Peroxide

AbstractThe hydrogen peroxide (H2O2) produced through electrochemical two‐electron oxygen reduction reaction (2e− ORR) is a promising green synthesis method and served as potential strategy to replace the energy‐intensive anthraquinone process. Nevertheless, the design of low‐cost and efficient electrocatalysts for 2e− ORR remains a formidable challenge. In this study, Sn‐BiOCl nanosheets electrocatalysts are prepared for expediting the 2e− ORR, achieving a high H2O2 selectivity of 92.9%, and the H2O2 yield of 10628 mg L−1 h−1 (0.1 mg cm−2) in a flow‐cell device. The in situ ATR‐SEIRAS results reveal that Sn‐BiOCl enhances the adsorption and activation of *OOH compared to BiOCl, resulting in higher activity and selectivity for 2e− ORR. Furthermore, this study investigates the potential for on‐site production and application of H2O2 using Sn‐BiOCl, which displays a 95% degradation removal of dyes (RhB, MB, and MO) within 20 min. This work not only have an insight into the critical roles of Bi and Sn atoms in enhancing the catalytic performance but also provides a thought to design efficient catalysts for production H2O2 via electrochemical 2e− ORR.

Zn-O-Sn covalency interface governs the intrinsic activity of the Zn2SnO4/SnO2 heterostructure for boosting hydrogen peroxide production

Electrocatalytic production of hydrogen peroxide (H2O2) from oxygen is vital for sustainable clean fuel. Developing highly active, stable, and inexpensive catalysts for H2O2 remains a top priority but is still challenging. In this study, an atomic-shared heterointerface was constructed between Zn2SnO4 and SnO2 via a self-templating co-precipitation method. Theoretical and experimental analysis confirms the delocalization effects of electrons within the Zn2SnO4/SnO2 spinel structure. The resulting Zn-O-Sn bridge (asymmetric sites) modulates electronic transport at the interface, and the intensified Zn-O bond facilitates proton adsorption and transfer kinetics. Moreover, strong interface coupling between Zn2SnO4 and SnO2 enhances electron transfer, which effectively promotes the *OOH intermediate favorable for H2O2 production, boosting H2O2 selectivity of nearly 97 %. The high production rate of 8.19 mol gcat−1 h−1 and excellent stability during long-term operation over 24 h. This work provides strategic insights into developing efficient H2O2 catalysts and other catalytic applications.

Spin Manipulation of Heterogeneous Molecular Electrocatalysts by an Integrated Magnetic Field for Efficient Oxygen Redox Reactions.

Understanding the spin-dependent activity of nitrogen-coordinated single metal atom (M-N-C) electrocatalysts for oxygen reduction and evolution reactions (ORR and OER) remains challenging due to the lack of structure-defined catalysts and effective spin manipulation tools. Herein, both challenges using a magnetic field integrated heterogeneous molecular electrocatalyst prepared by anchoring cobalt phthalocyanine (CoPc) deposited carbon black on polymer-protected magnet nanoparticles, are addressed. The built-in magnetic field can shift the Co center from low- to high-spin (HS) state without atomic structure modification, affording one-order higher turnover frequency, a 50% increased H2O2 selectivity for ORR, and a ≈4000% magnetocurrent enhancement for OER. This catalyst can significantly minimize magnet usage, enabling safe and continuous production of a pure H2O2 solution for 100 h from a 100 cm2 electrolyzer. The new strategy demonstrated here also applies to other metal phthalocyanine-based catalysts, offering a universal platform for studying spin-related electrochemical processes.

Synergistic Active Heterostructure Design for Enhanced Two Electron Oxygen Reduction via Chemical and Electrochemical Reconstruction of Heterosulfides

AbstractTransition metal sulfides, particularly heterostructures, represent a promising class of electrocatalysts for two electron oxygen reduction (2e− ORR), however, understanding the dynamic structural evolution of these catalysts during alkaline ORR remains relatively unexplored. Herein, NiS2/In2.77S4 heterostructure was synthesized as a precatalyst and through a series of comprehensive ex situ and in situ characterizations, including X‐ray absorption spectroscopy, Raman spectroscopy, transient photo‐induced voltage measurements, electron energy loss spectroscopy, and spherical aberration‐corrected electron microscopy, it was revealed that nickel/indium (oxy)hydroxides (NiOOH/In(OH)3) could be evolved from the initial NiS2/In2.77S4 via both electrochemical and chemical‐driven methods. The electrochemical‐driven phase featured abundant bridging oxygen‐deficient [NiO6]‐[InO6] units at the interfaces of NiOOH/In(OH)3, facilitating a synergistic effect between active Ni and In sites, thus enabling an enhanced alkaline 2e− ORR capability than that of chemical‐driven process. Remarkably, electrochemically induced NiOOH/In(OH)3 exhibited exceptional performance, achieving H2O2 selectivity of >90 % across the wide potential window (up to 0.4 V) with a peak selectivity of >99 %. Notably, within the three‐electrode flow cell, a current density of 200 mA cm−2 was sustained over 20 h, together with an impressive Faradaic efficiency of ~90 % during the whole cycle process.

Synergistic Active Heterostructure Design for Enhanced Two Electron Oxygen Reduction via Chemical and Electrochemical Reconstruction of Heterosulfides.

Transition metal sulfides, particularly heterostructures, represent a promising class of electrocatalysts for two electron oxygen reduction (2e- ORR), however, understanding the dynamic structural evolution of these catalysts during alkaline ORR remains relatively unexplored. Herein, NiS2/In2.77S4 heterostructure was synthesized as a precatalyst and through a series of comprehensive ex situ and in situ characterizations, including X-ray absorption spectroscopy, Raman spectroscopy, transient photo-induced voltage measurements, electron energy loss spectroscopy, and spherical aberration-corrected electron microscopy, it was revealed that nickel/indium (oxy)hydroxides (NiOOH/In(OH)3) could be evolved from the initial NiS2/In2.77S4 via both electrochemical and chemical-driven methods. The electrochemical-driven phase featured abundant bridging oxygen-deficient [NiO6]-[InO6] units at the interfaces of NiOOH/In(OH)3, facilitating a synergistic effect between active Ni and In sites, thus enabling an enhanced alkaline 2e- ORR capability than that of chemical-driven process. Remarkably, electrochemically induced NiOOH/In(OH)3 exhibited exceptional performance, achieving H2O2 selectivity of >90 % across the wide potential window (up to 0.4 V) with a peak selectivity of >99 %. Notably, within the three-electrode flow cell, a current density of 200 mA cm-2 was sustained over 20 h, together with an impressive Faradaic efficiency of ~90 % during the whole cycle process.

Accelerated Proton-Coupled Electron Transfer via Engineering Palladium Sub-Nanoclusters for Scalable Electrosynthesis of Hydrogen Peroxide.

Electrosynthesis of H2O2 from oxygen reduction reaction via a two-electron pathway is vital as an alternative for the energy-intensive anthraquinone process. However, this process is largely hindered in neutral and alkaline conditions due to sluggish kinetics associated with the transformation of intermediate O2* into OOH* via proton-coupled electron transfer sourced from slow water dissociation. Herein, we developed Pd sub-nanoclusters on the nickel ditelluride nanosheets (Pd SNCs/NiTe2) to enhance the performance of H2O2 electrosynthesis. The newly-developed Pd SNCs/NiTe2 exhibited a H2O2 selectivity of as high as 99% and a positive shift of onset potential up to 0.81 V. Combined theoretical calculations and experimental studies (e.g., X-ray absorption and attenuated total reflectance-Fourier transform infrared spectra measurements) revealed that the Pd sub-nanoclusters supported by NiTe2 nanosheets efficiently reduced the energy barrier of water dissociation to generate more protons, facilitating the proton feeding kinetics. When used in a flow cell, Pd SNCs/NiTe2 cathode efficiently produced H2O2 with a maximum yield rate of 1.75 mmol h-1 cm-2 and current efficiency of 95% at 100 mA cm-2. Further, an accumulated H2O2 concentration of 1.43 mol L-1 was reached after 10 hours of continuous electrolysis, showing the potential for practical H2O2 electrosynthesis.