Nickel Oxide Application Principle

Nickel oxide (NiO) is an important transition metal oxide with unique catalytic, electrochemical, magnetic and other properties. It is widely used in batteries, catalysts, electronic materials and other fields. Its core application principle is as follows:

1. Lithium ion batteries (electrode materials)

Application:

-Used as a cathode material (partially specially designed) or cathode dopant (such as LiNiO₂^-based lithium batteries).

-A precursor for active substances in nickel metal hydride batteries (Ni^-MH).

Principle:

-Lithium storage mechanism (conversion reaction): NiO+2Li⁺+2e^-=Ni+LiO

-Charging: Li⁺ is embedded, NiO is reduced to metal Ni, and Li₂O is generated.

-During discharge: Ni is oxidized back to NiO and Li⁺ is released.

-Advantages: The theoretical specific capacity is high (718 mAh/g), but the volume expansion is large, so it needs to be combined with carbon materials to improve the cycling performance.

2. Catalysts

Application:

-Organic synthesis: catalytic hydrogenation, oxidation reactions (such as methane reforming to produce hydrogen).

-Environmental protection: automobile exhaust purification (CO and hydrocarbon oxidation).

Principle:

-Surface active sites: The d-electrons of Ni²⁺ participate in the adsorption and activation of reactants.

-Methane reforming to produce hydrogen (example): CH⁴+H₂O->CO+3H²

-NiO is reduced to Ni, providing an active metal site.

-CO oxidation: 2CO+O₂->2CO₂

-Oxygen vacancies in NiO promote O₂ dissociation.

3. Gas sensitive sensor

Application:

Detect flammable gas (H₂, CO) or toxic gas (NO₂).

Principle:

-Resistance change mechanism:

-When NiO is exposed to a reducing gas (such as H₂), the gas reacts with surface oxygen, releasing electrons and reducing resistance.

-For oxidizing gases (such as NO₂), increase the resistance.

-Advantages: high sensitivity and low cost, but heating (200~400℃) is required to improve the response speed.

4. Magnetic materials and electronic devices

Application:

-Spintronics: preparation of anti-ferromagnetic insulating films (the Niel temperature of NiO ~ 523K).

-Material sensitized solar cell (DSSC): for electrode materials.

Principle:

-Anti-ferromagnetism: The d⁸ electrons of Ni²⁺are arranged in an orderly spin order, with no net magnetic moment, but the exchange bias of the adjacent ferromagnetic layer can be regulated.

-Photoelectric conversion (in DSSC): I³+2e^-->3I^-

-NiO catalyzes the reduction of I₃⁻ in the electrolyte to complete the circuit cycle.

5. Coloring of ceramics and glass

Application:

-Ceramic glaze (green or black), glass filter (absorbs ultraviolet light).

Principle:

-Crystal field effect: Ni²⁺ d-d transition absorbs light at a specific wavelength (e.g., ~400nm, green).

-Stable at high temperature, no decomposition.

6. Supercapacitors

Application:

-As a pseudocapacitance material, it provides fast charge and discharge capability.

Principle:

-Surface REDOX reaction: NIO+OH^-->NiOOH+e^-

-In an alkaline electrolyte, NiO reacts reversibly with OH^-to store charge.

Attention:

-Toxicity: NiO dust inhalation may cause cancer (category IARC 2B), need protection.

-Stability: it may be reduced to metal Ni at high temperature (e.g., in H₂ environment).

-Nanization effect:Nano^-NiO has a large specific surface area and better catalytic/electrochemical performance, but it is easy to agglomeration.

Sum up:

The core applications of nickel oxide depends on its:

-Electrochemical activity (batteries, supercapacitors)

-Catalytic properties (hydrogenation, oxidation reactions)

-Magnetic and photoelectric properties (electronic devices, sensors)

-Future trends are in nanostructured design and composite material development (such as NiO/graphene) to improve performance.