Electronic Structure Regulation and Surface Reconstruction of Iron Diselenide for Enhanced Oxygen Evolution Activity

Pumping Electrons from Oxygen-Bridged Cobalt for Low-Charging-Voltage Zn-Air Batteries

Reducing the charging voltage is a prerequisite for improving the chargeability and energy efficiency of Zn-air batteries (ZABs). Herein, Fe3+ pumps electrons from oxygen-bridged cobalt (Fe-O-Co) and induces the accelerated charging kinetics. For the liquid ZABs, a charging voltage of around 1.94 V at 10 mA cm-2 was displayed, which slightly increased 2% after continuous cycles for 180 h. A steady charging voltage of around 1.87 V at 10 mA cm-2 was also exhibited for quasi-solid-state ZABs. Control experiments and characterization show that the interactions between the O2- and Fe3+ sites are relatively weaker than those between the O2- and Co3+ sites. Compared with Mn3+, Zn2+, and Cu2+, Fe3+ effectively pumps electrons from Co sites to generate the active species for the oxygen evolution reaction. Thus, the deprotonation behavior and *OH conversion were improved. This work demonstrates the oxygen electron bridge modulated electron transfer between dual metal sites, contributing to the improvement of low-charging-voltage ZABs.

Activating and Stabilizing Lattice Oxygen via Self-Adaptive Zn-NiOOH Sub-Nanowires for Oxygen Evolution Reaction

Efficient and durable catalysts for the oxygen evolution reaction are essential for realizing the large-scale application of water electrolysis technologies. Here, we report a novel Zn-doped NiOOH subnanowires (Zn-NiOOH SNWs) catalyst synthesized via the electrochemical reconstruction of Zn-NiMoO4 SNWs. The inclusion of Zn triggers a transition in the oxygen evolution reaction mechanism of NiOOH from the adsorbate evolution mechanism to the lattice oxygen mechanism, resulted from Zn's adaptive adjustment of coordination types, which also improves the reaction energetics, thereby enhancing the stability and activity. Furthermore, the subnanowire structure provides further stabilization of the lattice oxygen in Zn-NiOOH, preventing its destructive dissolution. Remarkably, Zn-NiOOH SNWs display a current density of 10 mA cm-2 with an overpotential of only 179 mV and maintain stable operation at 200 mA cm-2 for 800 h with minimal changes in overpotential, establishing them as one of the most effective catalysts involving lattice oxygen for the alkaline oxygen evolution reaction. When utilized as the anode in an alkaline water electrolyzer, our Zn-NiOOH SNWs catalyst demonstrates stability exceeding 500 h under a water-splitting current of 200 mA cm-2, indicating promising potential for practical applications.

Cr doping and heterostructure-accelerated NiFe LDH reaction kinetics assist the MoS2 oxygen evolution reaction

Although molybdenum disulfide (MoS2) has garnered significant interest as a potential catalyst for the oxygen evolution reaction (OER), its poor intrinsic activity and few marginal active spots restrict its electrocatalytic activity. Herein, we successfully constructed a catalyst via a simple hydrothermal method by forming a heterostructure of MoS2 with Cr-doped nickel-iron hydroxide (NiFe LDH) to synthesize a MoS2/NiFeCr LDH catalyst to significantly improve the OER catalytic performance. MoS2 plays a crucial function as an electron transport channel in the MoS2/NiFeCr LDH heterostructure, which increases the electron transport rate. Furthermore, a larger active surface area for NiFeCr LDH is provided by the ultrathin layered structure of MoS2, increasing the number of active sites and encouraging the OER. On the other hand, the introduction of Cr element increased the density of the catalytic center and provided additional Cr-OH active sites, which accelerated the oxygen decomposition reaction. These two factors act synergistically to improve the intrinsic structure of MoS2, increase the number of reactive sites, and dramatically enhance the OER catalytic performance. Excellent OER activity is demonstrated by the MoS2/NiFeCr LDH catalyst, which only needs an overpotential of 224 mV to obtain a current density of 10 mA cm-2 and a Tafel slope of 61 mV dec-1. The catalyst also demonstrated outstanding stability, with its activity practically holding steady after 48 h of testing. This work offers novel ideas for enhancing and designing MoS2-based OER catalysts, and it provides a crucial reference for research in the field of clean energy.