Nickel Nanoparticles Encapsulated in Nitrogen‐Doped Carbon Nanofibers as Excellent Bifunctional Catalyst for Hydrogen and Oxygen Evolution Processes

Abstract

The potential of nitrogen-doped carbon nanofibers with encapsulated Ni nanoparticles as a bifunctional catalyst in H 2 and O 2 evolution reactions (HER and OER, respectively) was studied. The proposed heterostructure is fabricated via a facile chemical vapor deposition on Ni supported on graphitic carbon nitride (GCN) as a precursor. HER was an effect of photocatalytic water splitting and catalytic dehydrogenation of lactic acid used as sacrificial electron donor. However, photocatalysis played the dominant role in the acceleration of the reaction rate which was 17 times and 330 times higher in respect to the sample prior the CVD and to pristine GCN, respectively. The catalyst exhibited boosted electrocatalytic activity in OER and outstanding stability in respect to RuO 2 in alkaline medium. The overpotentials calculated from linear sweep voltammetry at 10 mA cm À 2 is ~383 mV for the fabricated electrocatalyst in respect to 490 mV for the RuO 2 and Tafel slope is calculated to be 106 mV dec À 1 in comparison to 136 mV dec À 1 for the reference which is above the state-of the-art bifunctional catalysts reported to date. The results reveal that the catalytic processes were boosted due to several key effects such as enhanced visible light absorption, better charge carriers transfer and separation, increased free charge carrier concentration and higher reducing ability of electrons.

Nitrogen‐Doped Electrocatalysts, and Photocatalyst in Water Splitting: Effects, and Doping Protocols

“…To raise the mass transfer, the surface area of the electrocatalyst needs to be increased by controlling the synthesis procedure to obtain porous or nanoscale materials [15l] . Carbon nanosheet, CNT, graphene, and rGO are some instances in this area, in which their composites’ high activities as the electrocatalysts are attributed to the high surface area in addition to the direct N effects (Tables 1, and 2) [15‐38] …”

Synergistic Coupling of Hierarchical Heterostructured Ni3P/Ni/VN Microflower Electrocatalyst for Enhanced Hydrogen Evolution Reaction

“…[1][2][3] With the advantages of zero emissions, high purity and high efficiency, water electrolysis is widely acknowledged as the most promising approach to supply hydrogen energy in the future. [4][5][6] However, the cathodic hydrogen evolution reaction (HER) involves a multi-step proton coupling process, in which the high overpotential and sluggish kinetics gravely diminish the overall energy conversion efficiency. [7][8][9] Moreover, it is highly important for the catalysts to play a positive role in a wide pH range in order to meet different applications.…”

“…Hydrogen energy has attracted widespread attention as secondary energy with abundant sources, green, low carbon and versatile application and its exploitation has become one of the effective ways to cope with the worsening energy crisis and environmental pollution problems, and is of great significance to the achievement of the “carbon peaking” and “carbon neutrality” targets [1–3] . With the advantages of zero emissions, high purity and high efficiency, water electrolysis is widely acknowledged as the most promising approach to supply hydrogen energy in the future [4–6] . However, the cathodic hydrogen evolution reaction (HER) involves a multi‐step proton coupling process, in which the high overpotential and sluggish kinetics gravely diminish the overall energy conversion efficiency [7–9] .…”

Simple Method to Enhance the Oxidation–Reduction Reaction Activity of a Carbon Nanotube-Based Nickel–Iron Layered Double Hydroxide as a Bifunctional Electrocatalyst

“…Currently, the creation of alternative sustainable green energies with high performance is a strong social demand, which is one of the crucial targets in the SDGs action platforms, and promising alternative energy technologies are batteries, fuel cells, supercapacitors, and solar energy in addition to natural energy, such as wind power, geothermal power generation, etc. The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) occur with very sluggish kinetics; − however, efficient and durable ORR/OER bifunctional electrocatalysts are very important for lowering the overpotentials to improve the energy conversion efficiency of industry-demanded rechargeable metal-air batteries and reversible fuel cells, water electrolyzers, and smart-grid energy storage systems for commercialization. Precious-metal-based catalysts, such as nanoparticles of Pt and IrO 2 , have been well known as excellent electrocatalysts for the ORR and OER, respectively .…”

“…Precious-metal-based catalysts, such as nanoparticles of Pt and IrO 2 , have been well known as excellent electrocatalysts for the ORR and OER, respectively . Considering the cost and source scarcity, however, the development of non-precious-metal catalysts from earth-abundant elements, such as iron (Fe), nickel (Ni), and/or Ti including transition-metal chalcogenides, oxides, nitrides, doped nanocarbon materials, metal macrocycles, etc., is in high demand from industry. − Many papers describing advances involving ORR and OER electrocatalysis mainly using non-precious-metal catalysts have been published. − …”