Spin-Magnetic Effect of d-π Conjugation Polymer Enhanced O-H Cleavage in Water Oxidation.

A deep understanding of the mechanism for the spin-magnetic effect on O-H cleavage is crucial for the development of new catalysts for water oxidation. Herein, we designed and synthesized the crystalline Fe-DABDT and Co-DABDT (DABDT = 2,5-diaminobenzene-1,4-dithiol) and optimized an effective magnetic moment to explore the role of the spin-magnetic effect in the regulation of water oxidation activity. It can be found that the OER activity of the catalyst is positively correlated with its effective magnetic moment. Under the external magnetic field, Fe-DABDT with more spin single electrons has a stronger spin-magnetic response to water oxidation than Fe/Co-DABDT and Co-DABDT. The increase in OER current of Fe-DABDT is nearly 2 times higher than that of Co-DABDT. Experimental and density functional theory studies show that magnetized Fe sites could realize nucleophilic reaction, accelerate the polarization of electron spin states, and promote the polar decomposition of O-H and the formation of the O-O bond. This study provides mechanistic insight into the spin-magnetic effect of oxygen evolution reaction and further understanding of the spin origin of catalytic activity, which is expected to improve the energy efficiency of hydrogen production.

Single-Atom Mn Catalysts via Integration with Mn Sub Nano-Clusters Synergistically Enhance Oxygen Reduction Reaction.

Integrating single atoms and clusters into one system represents a novel strategy for achieving the desired catalytic performance. In comparison to single-atom catalysts, catalysts combining single atoms and clusters harness the advantages of both, thus displaying greater potential. Nevertheless, constructing single-atom-cluster systems remains challenging, and the fundamental mechanism for enhancing catalytic activity remains elusive. In this study, a directly confined preparation of a 3D hollow sea urchin-like carbon structure (MnSA/MnAC-SSCNR) is developed. Mn single atoms synergistically interact with Mn clusters, optimizing and reducing energy barriers in the reaction pathway, thus enhancing reaction kinetics. Consequently, in contrast to Mn single-atom catalysts (MnSA-SSCNR), MnSA/MnAC-SSCNR exhibits significantly improved oxygen reduction activity, with a half-wave potential (E1/2) of 0.90 V in 0.1 m KOH, surpassing that of MnSA-SSCNR and Pt/C. This work demonstrates a strategy of remote synergy between heterogeneous single atoms and clusters, which not only contributes to electrocatalytic reactions but also holds potential for reactions involving more complex products.

Open Active Sites in Ni-Based MOF with High Oxidation States for Electrooxidation of Benzyl Alcohol.

The kinetics of electrocatalytic reactions are closely related to the number and intrinsic activity of the active sites. Open active sites offer easy access to the substrate and allow for efficient desorption and diffusion of reaction products without significant hindrance. Metal-organic frameworks (MOFs) with open active sites show great potential in this context. To increase the density of active sites, trimesic acid was utilized as a ligand to anchor more Ni sites and in situ construct the nickel foam-loaded Ni-based trimesic MOF electrocatalyst (Ni-TMA-MOF/NF). When tested as an electrocatalyst for benzyl alcohol oxidation, Ni-TMA-MOF/NF exhibited lower overpotential and superior durability compared to Ni foam-loaded Ni-based terephthalic MOF electrocatalyst (Ni-PTA-MOF/NF) and Ni(OH)2 nanosheet array (Ni(OH)2/NF). Ni-TMA-MOF/NF required only a low potential of 1.65 V to achieve a high current density of 400 mA cm-2. Even after 40000 s of electrocatalytic oxidation at 1.5 V, Ni-TMA-MOF/NF maintained a current density of 175 mA cm-2 with ∼68% retention, showing its potential for benzyl alcohol oxidation. Through a combination of experimental and theoretical investigations, it was found that Ni-TMA-MOF/NF displayed superior electrocatalytic activity due to an optimized electron structure with high-valence Ni species and a high density of active sites, enabling long-term stable operation at high current densities. This study provides a new perspective on the design of electrocatalysts for benzyl alcohol oxidation.

Efficient H2O2 Synthesis through a Two-Electron Oxygen Reduction Reaction by Electrocatalysts.

The two-electron oxygen reduction reaction (2e-ORR) for the sustainable synthesis of hydrogen peroxide (H2O2) has demonstrated considerable potential for local production of this environmentally friendly chemical oxidant on small, medium, and large scales. This method offers a promising alternative to the energy-intensive anthraquinone approach, placing a primary emphasis on the development of efficient electrocatalysts. Improving the efficiency of electrocatalysts and uncovering their catalytic mechanisms are essential steps in achieving high 2e-ORR activity, selectivity, and stability. This comprehensive review summarizes recent advancements in electrocatalysts for in-situ H2O2 production, providing a detailed overview of the field. In particular, the review delves into the design, fabrication, and investigation of catalytic active sites contributing to H2O2 selectivity. Additionally, it highlights a range of electrocatalysts including pure metals and alloys, transition metal compounds, single-atom catalysts, and carbon-based catalysts for the 2e-ORR pathway. Finally, the review addresses significant challenges and opportunities for efficient H2O2 electrosynthesis, as well as potential future research directions.

Highly Ordered Hierarchical Macro-Mesoporous Carbon-Supported Cobalt Electrocatalyst for Efficient Oxygen Evolution Reaction.

Metal-organic frameworks (MOFs) and their derivatives have been extensively employed in Oxygen Evolution Reaction (OER) catalysts due to their significantly larger specific surface areas, distinct metal centers, and well-organized porous structures. However, the microporous structure of MOFs and their derivatives presents mass transfer resistance, limiting their further development. Drawing inspiration from hierarchical structures allowing for the transport and exchange of substances in the biological world, we designed and fabricated biomimetic layered porous structures within ZIF-67 and its derivatives. Based on this, we achieved a three-dimensional ordered layered porous nitrogen-doped carbon-coated magnetic cobalt catalyst (3DOLP Co@NDC) with a biomimetic pore structure. It is found that the 3DOLP Co@NDC (352 mV @10 mA cm-1) was better than Co@NDC (391 mV @10 mA cm-1). The introduction of a three-dimensional ordered layered porous structure is conducive to increasing the specific surface area of the material, increasing the electrochemical active area, and improving the catalytic performance of the material. The introduction of a three-dimensional ordered layered porous structure would help to build a bionic grade pore structure. The existence of biomimetic grade pore structure can effectively reduce the mass transfer resistance, improve the material exchange efficiency, and accelerate the reaction kinetics.