Synergistic Hybrid Support Comprising TiO2–Carbon and Ordered PdNi Alloy for Direct Hydrogen Peroxide Synthesis

Heteroatom-Coordinated Palladium Molecular Catalysts for Sustainable Electrochemical Production of Hydrogen Peroxide

Currently, hydrogen peroxide (H2O2) manufacturing involves an energy-intensive anthraquinone technique that demands expensive solvent extraction and a multistep process with substantial energy consumption. In this work, we synthesized Pd-N4-CO, Pd-S4-NCO, and Pd-N2O2-C single-atom catalysts via an in situ synthesis approach involving heteroatom-rich ligands and activated carbon under mild reaction conditions. It reveals that palladium atoms interact strongly with heteroatom-rich ligands, which provide well-defined and uniform active sites for oxygen (O2) electrochemically reduced to hydrogen peroxide. Interestingly, the Pd-N4-CO electrocatalyst shows excellent performance for the electrocatalytic reduction of O2 to H2O2 via a two-electron transfer process in a base electrolyte, exhibiting a negligible amount of onset overpotential and >95% selectivity within a wide range of applied potentials. The electrocatalysts based on the activity and selectivity toward 2e- ORR follow the order Pd-N4-CO > Pd-N2O2-C > Pd-S4-NCO in agreement with the pull-push mechanism, which is the Pd center strongly coordinated with high electronegativity donor atoms (N and O atoms) and weakly coordinated with the intermediate *OOH to excellent selectivity and sustainable production of H2O2. According to density functional theory, Pd-N4 is the active site for selectivity toward H2O2 generation. This work provides an emerging technique for designing high-performance H2O2 electrosynthesis catalysts and the rational integration of several active sites for green and sustainable chemical synthesis via electrochemical processes.

Pd-Sn Alloy Catalysts for Direct Synthesis of Hydrogen Peroxide from H2 and O2 in a Microchannel Reactor

Direct synthesis of hydrogen peroxide (DSHP) from H₂ and O₂ offers a promising alternative to the present commercial anthraquinone method, but it still faces the challenges of low H₂O₂ productivity, low stability of catalysts, and high risk of explosion. Herein, by loading in a microchannel reactor, the as-synthesized Pd-Sn alloy materials exhibit high catalytic activity for H₂O₂ production, presenting a H₂O₂ productivity of 3124 g kg_Pd^-1 h^-1. The doped Sn atoms on the surface of Pd not only facilitate the release of H₂O₂ but also effectively slow down the deactivation of catalysts. Theoretical calculations demonstrate that the Pd-Sn alloy surface has the property of antihydrogen poisoning, showing higher activity and stability than pure Pd catalysts. The deactivation mechanism of the catalyst was elucidated, and the online reactivation method was developed. In addition, we show that the long-life Pd-Sn alloy catalyst can be achieved by supplying an intermittent flow of hydrogen gas. This work provides guidance on how to prepare high performance and stable Pd-Sn alloy catalysts for the continuous and direct synthesis of H₂O₂.

Multiple Roles of Alkanethiolate-Ligands in Direct Formation of H2 O2 over Pd Nanoparticles

Coadsorbed organic species including thiolates can promote direct synthesis of hydrogen peroxide from H₂ and O₂ over Pd particles. Here, density functional theory based kinetic modeling, augmented with activity measurements and vibrational spectroscopy are used to provide atomistic understanding of direct H₂ O₂ formation over alkylthiolate(RS) Pd. We find that the RS species are oxidized during reaction conditions yielding RSO₂ as the effective ligand. The RSO₂ ligand shows superior ability for proton transfer to the intermediate surface species OOH, which accelerates the formation of H₂ O₂ . The ligands promote the selectivity also by blocking sites for unselective water formation and by modifying the electronic structure of Pd. The work rationalizes observations of enhanced selectivity of direct H₂ O₂ formation over ligand-funtionalized Pd nanoparticles and shows that engineering of organic surface modifiers can be used to promote desired hydrogen transfer routes.

Intrinsic Carbon Defects for the Electrosynthesis of H2O2

Carbon materials have manifested promising potential in electrochemical reduction of O₂ to H₂O₂. The oxygen functional groups have been identified as the catalytic sites. However, the intrinsic carbon defects abundant in carbon materials have often been neglected. Herein, a three-dimensional carbon framework with abundant intrinsic defects and oxygen functional groups (the oxygen content and chemical states of oxygen are comparable to those of commercial carbon black) was introduced and exhibited outstanding catalytic activity and selectivity toward H₂O₂ electrosynthesis. Through a combination of in situ Raman spectroscopy and density functional theory calculations, the intrinsic carbon defects, such as zigzag edge and zigzag pentagon sites with optimal binding energy for OOH, were also determined to be active sites. It was further revealed that intrinsic carbon defects with large negative charge density and asymmetric spin density may have high activity toward H₂O₂ production.

High-Efficiency Oxygen Reduction to Hydrogen Peroxide Catalyzed by Oxidized Mo2TiC2 MXene

The two-electron oxygen reduction reaction (2e−ORR) pathway electrochemical synthesis to H2O2 has the advantages of low investment and environmental protection and is considered to be a promising green method. Herein, the oxidized Mo2TiC2 MXene (O-Mo2TiC2) was successfully synthesized by a facile hydrothermal method as an electrocatalyst in electrocatalytic H2O2 production. The O-Mo2TiC2 achieved the 90% of H2O2 selectivity and 0.72 V vs. RHE of the onset potential. Moreover, O-Mo2TiC2 showed high charge transfer ability and long-term stable working ability of 40 h. This significantly enhanced electrocatalytic H2O2 production capacity is assigned the oxidation treatment of Mo2TiC2 MXene to generate more oxygen-containing groups in O-Mo2TiC2. This work provides a promising catalyst candidate for the electrochemical synthesis of H2O2.

Enhancing the catalytic performance of PdAu catalysts by W-induced strong interaction for the direct synthesis of H2O2

W-Induced strong interaction with PdAu is the key to the enhanced catalytic performance for the direct synthesis of H2O2, with WO3 species partially encapsulating the PdAu particles.

Bimetallic Nanocrystals: Structure, Controllable Synthesis and Applications in Catalysis, Energy and Sensing

In recent years, bimetallic nanocrystals have attracted great interest from many researchers. Bimetallic nanocrystals are expected to exhibit improved physical and chemical properties due to the synergistic effect between the two metals, not just a combination of two monometallic properties. More importantly, the properties of bimetallic nanocrystals are significantly affected by their morphology, structure, and atomic arrangement. Reasonable regulation of these parameters of nanocrystals can effectively control their properties and enhance their practicality in a given application. This review summarizes some recent research progress in the controlled synthesis of shape, composition and structure, as well as some important applications of bimetallic nanocrystals. We first give a brief introduction to the development of bimetals, followed by the architectural diversity of bimetallic nanocrystals. The most commonly used and typical synthesis methods are also summarized, and the possible morphologies under different conditions are also discussed. Finally, we discuss the composition-dependent and shape-dependent properties of bimetals in terms of highlighting applications such as catalysis, energy conversion, gas sensing and bio-detection applications.