Highly Effective OER Electrocatalysts Generated from a Two-Dimensional Metal–Organic Framework Including a Sulfur-Containing Linker without Doping

Abstract

Metal−organic frameworks (MOFs) with different topologies formed by the self-assembly of sulfur-containing inorganic ligands, cobalt ions, and large ligands can be used to prepare electrocatalysts for water splitting in order to fully explore the advantages of MOFs in terms of structural tailoring and quantitative assembly. It is possible to avoid using an extradoped sulfur source to reduce waste as well as to disperse Co and sulfur elements evenly and controllably throughout the final material to maximize the overall synergistic effect. In this work, different kinds of bimetallic MOF materials containing sulfur can be synthesized very conveniently by using an economical and practical diffusion method. These materials are directly used as OER electrocatalysts, and the bimetallic MOFs have the best electrocatalytic performance when the ratio of Co to Fe is 6:4. The overpotential at a current density of 10 mA cm −2 was 260 mV, with a Tafel slope of 56 mV dec −1 and good stability. It was assembled with 20% commercial Pt/C material into a two-electrode system for all-water decomposition, and the decomposition voltage at 10 mA cm −2 was 1.81 V. From the electronic configuration microscopic point of view, the introduction of iron ions changed the original synergistic effect for Co−S−Co, which more easily led to the formation of high-valence Co 3+ and finally produced highly active electrocatalytic sites. From a macroscopic point of view, the material produced in situ during the electrochemical reaction process not only retains the original 2D layered structure but also utilizes bubbles to produce a loose structure with defective sites. These structural features are advantageous because they provide not only an abundance of active sites and permeable channels but also the necessary interfaces and electron-transport channels for the formation of electrostatic charge-separation layers, making it easier to intercalate and delaminate the hydroxide ions. Furthermore, the changed hydroxyl ions and nitrogen and sulfur atoms on the channel surface may operate as interaction sites, increasing the surface characteristics, facilitating electron transfer, and reducing electron-transfer resistance. To summarize, the rational design of sulfurcontaining layered MOF materials directly as water-splitting catalysts is a crucial next step in developing cost-effective, environmentally friendly, and low-energy-consumption electrocatalysts based on the findings of this study.

Manganese–cobalt hydroxide nanosheets anchored on a hollow sulfur-doped bimetallic MOF for high-performance supercapacitors and the hydrogen evolution reaction in alkaline media

“…1,2 The global energy crisis and serious environmental pollution have prompted researchers to explore clean energy and energy storage equipment to protect the global environment while developing the economy. [3][4][5] Excellent energy storage equipment can not only solve the sustainability problem of intermittent clean energy sources such as hydrogen energy, wind energy, solar energy, and tidal energy, [6][7][8] but can also improve effective utilization and save energy. In recent years, fuel cells, rechargeable batteries, supercapacitors and other types of excellent energy storage equipment have been widely used in industry, such as automotive, electronics, medicine and other industries.…”

Realizing a Lattice Se Atom-Modified Co Hydroxide Catalyst via Electrochemical Reconstruction for Enhanced Oxygen Evolution Performance

“…With the rapid development of human society, excessive consumption of fossil fuels has caused serious energy crises and environmental concerns. It is particularly vital to seek sustainable, clean, and efficient technologies to resolve energy and environmental problems. − Electrochemical water splitting has attracted wide attention as the most potent way to produce hydrogen energy instead of traditional hydrogen production. , Typically, electrochemical water splitting comprises two half-reactions including the anodic oxygen evolution reaction (OER) with a four-electron transfer and the cathodic hydrogen evolution reaction (HER) with a two-electron transfer. − Because of the intricate reaction pathways and complex oxygen-involving intermediates, the reaction kinetics of OER is sluggish and requires a high overpotential to overcome the reaction energy barrier. Hence, developing highly efficient OER catalysts is essential for the further application of OER and water splitting. , Among various candidates, catalysts based on noble metals, such as Ru and Ir, exhibit the ideal performance toward OER. − However, their scarcity and high price hinder their widespread generalization.…”

Self-Reconstruction of Fe-Doped Co-Metal–Organic Frameworks Boosted Electrocatalytic Performance for Oxygen Evolution Reaction

“…Developing new technologies to obtain renewable energy and exploiting alternatives to fossil fuels have drawn global interest with ever-growing global energy demand and environmental degradation. − Electrocatalytic oxygen evolution reaction (OER) plays a crucial part in renewable-energy conversion and storage technologies, like metal–air batteries, water electrolysis, and fuel cells. − Nevertheless, the OER has sluggish kinetics as a result of the four-electron proton coupling process in alkaline media, which usually causes high overpotentials, greatly reducing the energy conversion efficiency of the equipment. − As a result, effective electrocatalysts for OER (2H 2 O → O 2 + 4H + +4e – ) have been thoroughly investigated to overcome the sluggish OER process. To date, Ir- and Ru-based catalysts are still recognized as state-of-the-art OER electrocatalysts, but their disadvantages of inherent scarcity, low stability, and high expense badly hindered their industrialization. − Consequently, a key target for researchers is to design and develop a nonprecious metal-based OER electrocatalyst with low expenses, high catalytic activity, and robust durability, as well as understand the underlying mechanism. − The corresponding design will be developed based on several considerations, including suitable dimensionality and morphology, favorable conductivity, and numerous exposed active sites, among others. , …”