Interface Electronic Modulation of Monodispersed Co Metal-Co₇Fe₃ Alloy Heterostructures for Rechargeable Zn–Air Battery

Engineering heterointerfaces between metal and alloy to facilitate charge transfer would be an attractive strategy for superefficient electrocatalysis. Herein, a simple xerogel-pyrolysis strategy has been designed to prepare an advanced bifunctional electrocatalyst, Co/Co7Fe3 confined by a porous N-doped carbon nanosheets/CNTs composite (Co/Co7Fe3@PNCC). The formative Co/Co7Fe3 heterostructure promoted the charge transfers from metal Co to active alloy Co7Fe3, thus reducing the energy barrier of the oxygen reduction reaction and improving the catalytic kinetics and active surface area for the oxygen evolution reaction. The PNCC provided monodispersed confined space for Co/Co7Fe3 particles, which also owned a high specific surface area for ions/gases diffusion. Therefore, Co/Co7Fe3@PNCC exhibited excellent bifunctional oxygen catalysis activities and durability with an ultralow polarization gap (ΔE) of only 0.64 V. When practically adopted as an air electrode in ZAB, a large open-circuit voltage of 1.534 V, a maximum power density of 211.82 mW cm–2, an ultrahigh specific capacity of 807.33 mAh g–1, and superior durability over 800 h were obtained. This catalyst design concept offers a facile strategy toward modulating electronic structure to achieve efficient bifunctional electrocatalysts for ZAB

Alternating Magnetic Field Induced Magnetic Heating in Ferromagnetic Cobalt Single-Atom Catalysts for Efficient Oxygen Evolution Reaction

Alternating magnetic field (AMF) is a promising methodology for further improving magnetic single-atom catalyst (SAC) activity toward oxygen evolution reaction (OER). Herein, the anchoring of Co single atoms on MoS2 support (Co@MoS2), leading to the appearance of in-plane room-temperature ferromagnetic properties, is favorable for the parallel spin arrangement of oxygen atoms when a magnetic field is applied. Moreover, field-assisted electrocatalytic experiments confirmed that the spin direction of Co@MoS2 is changing with the applied magnetic field. On this basis, under AMF, the active sites in ferromagnetic Co@MoS2 were heated by exploiting the magnetic heating generated from spin polarization flip of these SACs to further expedite OER efficiency, with overpotential at 10 mA cm–2 reduced from 317 mV to 250 mV. This work introduces a feasible and efficient approach to enhance the OER performance of Co@MoS2 by AMF, shedding some light on the further development of magnetic SACs for energy conversion

Efficient Charge Transfers in Highly Conductive Copper Selenide Quantum Dot-Confined Catalysts for Robust Oxygen Evolution Reaction

Defective quantum dots (QDs) are the emerging materials for catalysis by virtue of their atomic-scale size, high monodispersity, and ultra-high specific surface area. However, the dispersed nature of QDs fundamentally prohibits the efficient charge transfer in various catalytic processes. Here, we report efficient and robust electrocatalytic oxygen evolution based on defective and highly conductive copper selenide (CuSe) QDs confined in an amorphous carbon matrix with good uniformity (average diameter 4.25 nm) and a high areal density (1.8 × 1012 cm–2). The CuSe QD-confined catalysts with abundant selenide vacancies were prepared by using a pulsed laser deposition system benefitted by high substrate temperature and ultrahigh vacuum growth conditions, as evidenced by electron paramagnetic resonance characterizations. An ultra-low charge transfer resistance (about 7 Ω) determined by electrochemical impedance spectroscopy measurement indicates the efficient charge transfer of CuSe quantum-confined catalysts, which is guaranteed by its high conductivity (with a low resistivity of 2.33 μΩ·m), as revealed by electrical transport measurements. Our work provides a universal design scheme of the dispersed QD-based composite catalysts and demonstrates the CuSe QD-confined catalysts as an efficient and robust electrocatalyst for oxygen evolution reaction