Electrospining: NiS2/NiS/Mn2O3 nanofibers with enhanced oxygen evolution reaction activity

Background

In recent years, it has been increasingly recognized that electrochemical water splitting is a viable method for producing clean, efficient, and sustainable hydrogen energy. Water electrolysis includes two main reactions: the cathode hydrogen evolution reaction (HER) and the anode oxygen evolution reaction (OER). OER is one of the two half reactions involved in the water electrolysis process. It involves the formation of two oxygen bonds and the transfer of multiple protons and electrons, which has a great influence on the reaction kinetics and catalytic efficiency. Efficient electrocatalysts are the key to accelerate OER. It is generally believed that precious metal materials such as RuO2 and IrO2 have high activity for OER. However, their use is limited by high cost and scarcity of precious metal elements in nature. Therefore, the fundamental goal of research and development on Earth is to study abundant, cost-effective and efficient transition metal-based electrocatalysts.

The main point of this paper

Background of the need for OER catalysts:

With the increasing demand for cost-effective and readily available materials as alternatives for OER catalysts, materials such as oxides, sulfides, selenides, nitrides and carbides of transition metals have attracted attention.

Advantages of Chalcogenides:

Chalcogenides, especially MSx, have become promising candidates for OER catalysts due to their excellent performance, stability and ease of preparation.

Challenges of OER:

As a complex four-electron transfer process, OER requires high energy input, especially due to the slow O-O bond formation step.

Role of Electrocatalysts:

Electrocatalysts promote OER by reducing the reaction overpotential and improving the reaction activity, and their performance is closely related to the number of active sites and intrinsic catalytic activity.

Importance of Structural Engineering:

Structural engineering, especially increasing the electrochemically active area and active site exposure, is an effective way to improve OER performance.

Design of nanostructures:

In order to improve the OER performance of sulfide compounds, a variety of nanostructures have been designed, including nanoparticles, nanosheets, nanowires and nanofibers, among which one-dimensional nanofiber structures have attracted attention due to their high specific surface area and abundant active sites.

One-dimensional NiS2/NiS/Mn2O3 nanofibers: Green hydrogen production catalysts for electrocatalytic water splitting

Advantages of NiS2/NiS/Mn2O3 nanofibers:

One-dimensional NiS2/NiS/Mn2O3 nanofibers prepared by electrospinning show excellent electrochemical performance in alkaline solution and can effectively improve the electrocatalytic performance of transition metal dichalcogenides

Electrocatalytic performance:

At a current density of 20 mA cm−2, OER requires an overpotential of 333 mV, showing electrocatalytic activity with low overpotential and high current density

Durability test:

NiS2/NiS/Mn2O3 nanofibers still maintain good durability after 1000 cycles, proving their stability

Long-term electrochemical stability:

At 20 mA In the 12-hour long-term electrochemical stability test under cm−2 conditions, the potential was maintained at 99.52%, indicating its excellent stability

Preparation method:

NiS2/NiS/Mn2O3 nanofibers prepared by electrospinning, thermal annealing and sulfurization show better charge/transport performance and a large number of electrocatalytic active sites due to their unique one-dimensional structure

Structural advantages:

The stacking of nanoparticles constructs NiS2/NiS/Mn2O3 nanofibers with a tough surface, exposing abundant interfacial active sites, and the one-dimensional nanostructure is conducive to barrier-free charge transmission and accelerates catalytic kinetics

Summarize

One-dimensional nanostructured NiS2/NiS/Mn2O3 catalysts were prepared by electrospinning. NiS2/NiS/Mn2O3 has a large specific surface area, increased electrolyte storage capacity and minimal electron transfer impedance. In our experiments, the one-dimensional NiS2/NiS/Mn2O3 nanofibers showed excellent OER (oxygen evolution reaction) activity. They only required an overpotential of 333 mV to achieve a current density of 20 mA cm-2 and showed excellent stability. This work provides a promising strategy for constructing durable OER catalysts.