Unlocking the Potential of Nickel Oxide

A Building Block of Innovation

Nickel oxide is a cornerstone compound across materials science and advanced engineering. Owing to its distinctive magnetic, electrical, thermal and surface-chemistry characteristics, it underpins research and industrial innovation across sectors spanning catalysis, electrochemistry, energy storage, and biomedicine. Crucially, these properties can be tuned through synthesis routes, stoichiometry and particle morphology, enabling researchers to match performance to purpose.

As production and refining technologies advance, the application opportunities for nickel oxide continues to expand. For academics and product developers alike, staying informed with material grades and processing trends is essential to experimental success and reliable scale-up.

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The Importance of Colour

Nickel oxide is commonly supplied in two principal forms whose stoichiometry and microstructure deliver distinct behaviours and suit different applications.

Green nickel oxide (NiO) is the more stable, stoichiometric variant. It is typically manufactured via thermal decomposition of nickel compounds (e.g., nickel carbonate or nickel nitrate), or by controlled oxidation of pure nickel at elevated temperatures. PI-KEM’s green nickel oxide contains 78.5% Ni by weight, and is available in several grades, with tailored particle sizes for precision applications. With its characteristic pale green colour and high purity, NiO is widely used in ceramics and glass colouration, as a precursor for catalysts and battery materials, and within solid oxide electrochemical devices. It best serves applications where consistency and reproducibility are essential.

Black nickel oxide (Ni₂O₃) is often produced under conditions that introduce non-stoichiometry and defect structures, yielding a darker powder with higher surface area and enhanced reactivity relative to the stoichiometric NiO. PI-KEM’s black nickel oxide contains 76.4–77.6% Ni by weight, and offers excellent thermal stability, oxidation resistance and electrical conductivity. These attributes make it advantageous in advanced catalysis, electrochemical energy storage and thin film electronics.

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While both materials are commonly discussed within the Ni(II) oxide family, differences in stoichiometry, defect chemistry and morphology drive their distinct appearances and functional properties. In practice, green and black nickel oxide provide a complementary toolkit, each optimised for specific research and industrial use cases.

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Industrial Origins

Nickel oxide's significance in industry originates from its broad utility across a range of scientific disciplines, from biology and chemistry, to engineering and electronics.

Nickel itself has a lengthy history of use, with evidence of its presence and alloying tracing back over 3500 years. Nickel was first isolated as an element in 1751 by Swedish chemist and minerologist Baron Axel Fredrik Cronstedt; the subsequent refining of the Mond process in 1890 enabled commercial-scale extraction and purification of nickel.

By the late 19th and early 20th centuries, nickel oxide had found widespread industrial use – most notably as a pigment, imparting reproducible green, brown or black hues to ceramics, glass, porcelain and enamel glazes. It remains a reliable colourant today, and features in advanced glass frit formulations that balance optical aesthetics (gloss, colour) with functional performance (thermal expansion, chemical durability, mechanical strength).

Nickel oxide has also played a role in the development of precision alloys. In 1920, the Nobel Prize in Physics recognised Charles Édouard Guillaume for nickel-steel alloys invar and elinvar, for which nickel oxide served as a precursor material during processing. Invar’s near zero coefficient of thermal expansion makes it valuable in precision instruments from clocks to cryogenic tools; elinvar’s near-zero thermal coefficient of the modulus of elasticity supports balance springs in devices such as seismographs and chronometers.

Energy storage is another longstanding application of nickel oxide. Early nickel-cadmium (Ni Cd) batteries utilised nickel oxyhydroxide derived from nickel oxide as the positive electrode during discharge. Although heavy, these cells proved durable for railway signalling and military uses, and later gained traction in consumer devices. They enjoyed widespread use in radios, power tools and cordless phones, and were valued for their long lifecycles.

By the late 20th century, concerns over the “memory effect” (a side effect of partial charging and discharging), cadmium toxicity and its environmentally damaging extraction process, saw Ni Cd usage decline. Environmental regulations reduced the prevalence of Ni-Cd batteries in consumer electronics, although they still appear in niche, specialised fields such as aviation, aerospace and tools operated in harsh environments. Instead, there was increased adoption of nickel-metal hydride (Ni MH) batteries and other chemistries, many of which still use nickel oxide as a key precursor material.

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Contemporary Applications

Nickel oxide remains central to modern industry and technology. Below we highlight several major application areas.

Solid Oxide Fuel Cells (SOFCs) and Solid Oxide Electrolyser Cells (SOECs)

• SOFCs are electrochemical cells that produce energy directly through the oxidation of a fuel, while SOECs electrolyse water to produce hydrogen. Green NiO plays a pivotal role in electrode structures (e.g., NiO based cermets), combining electronic conductivity with catalytic activity for the electrode half reactions. High operating temperatures enable excellent efficiency and fuel flexibility compared with low temperature alternatives, especially as they don’t require expensive platinum-group metal catalysts.

• SOFCs serve in stationary power generation, particularly as reliable backup for critical infrastructure such as hospitals. SOFCs also produce both electricity and useful heat, making them ideal for use in combined heat and power (CHP) systems, that utilise the excess heat for space and water heating; they provide excellent energy efficiency and lower emissions compare to traditional systems.

• SOECs support renewable energy integration by converting surplus electricity (generated from sources like wind or solar) into storable hydrogen; at peak usage times, it can be converted back to electricity to match demand. Reversible solid oxide cells (RSOCs) can function alternately as fuel cells or electrolysis cells, to balance energy generation and usage within the power grid.

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Catalysis

• Nickel oxide functions as a robust heterogeneous catalyst and catalyst support. Catalysts act to increase the rate of chemical reactions without being consumed in it, by providing an alternate reaction pathway with a lower activation energy.

• As a transition metal oxide, its variable oxidation states provide active sites for reaction, while controlled defects in the NiO lattice facilitate oxygen mobility, overall enhancing its catalytic function. High surface area powders further increase site density, while nickel oxide’s thermal stability underpins longevity.

• Nickel oxide can undergo oxidation and reduction cycles, losing or gaining electrons from other reactants; this makes it particularly useful to catalyse reactions involving transfers of electrons. It can also be used as a catalyst support in combination with other catalysts, such as cerium oxide or aluminium oxide.

• NiO is applied in hydrogenation and dehydrogenation reactions across alkenes, alkynes, aromatics and alcohols to produce valuable chemicals. It also supports oxidation catalysis, for example remediating environmentally harmful carbon monoxide in vehicle exhausts, and reforming light hydrocarbons to produce synthesis gas (a CO/H₂ mixture) for fuels and chemical feedstock. Additionally, its semiconductor properties enable nickel oxide to feature in photocatalytic systems for degrading dyes, pesticides and organic pollutants, including in water treatment contexts.

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Sensors and Smart Technologies

• Nickel oxide’s semiconducting, optical and surface properties lend themselves to sensing and optoelectronic devices.

• As a p-type semiconductor, holes are the main charge carrier across the material. A hole is the absence of an electron in the crystal’s atomic structure, and this vacancy can move through the material, behaving like a particle with a positive charge. Within nickel, this can be attributed to missing nickel atoms in its crystal structure. With a wide bandgap (~3.6–4.0 eV), NiO can conduct using holes while still being transparent to visible light and stable at high temperatures, making it useful in transparent electronics, solar cells, LEDs, and sensors.

• NiO thin films and nanostructures are deployed in gas sensors, where absorbed molecules alter electrical resistance by either donating or withdrawing electrons. Reducing gases, such as CO or CH4, will donate electrons and increase the conductivity, whereas oxidising gases, such as NO2, withdraw electrons and decrease conductivity. This behaviour can support environmental monitoring for harmful gases or pollution, controlling industrial processes, or detecting gases that pose risks to human health.

• Its temperature dependent conductivity enables usage in thermistors, including in harsh environments such as engines and furnaces. In electrochromic applications, NiO thin films reversibly change optical properties under applied voltage, forming the basis of smart windows, adaptive displays and mirrors. By adding other dopants to the film, the tint and its reactivity can be controlled. Pairing it with tungsten oxide produces a complementary electrochromic device, which includes one material that colours upon oxidation (nickel oxide) and another that colours upon reduction (tungsten oxide). These techniques allow tuning of colouration ranges, response times and durability.

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Metallurgical Processes

• Nickel oxide features in a number of metallurgical processes, primarily for the production and refining of metals and alloys.  It is an important intermediate in nickel extraction and refining, and a useful fluxing component in smelting. NiO serves as a precursor for nickel salts used in electroplating baths, enabling corrosion resistant or decorative coatings.

• As a feedstock for ferroalloys and superalloys, NiO supports alloy engineering for extreme environments such as power generation and aerospace. In refractories, its high melting point and chemical stability improve resistance to corrosion, wear and thermal shock in demanding furnace applications.

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Evolving Trends

The research scope for nickel oxide is vibrant, with several directions showing strong momentum across research and industry.

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Sustainable Synthesis

• Green routes to synthesising NiO nanoparticles are gaining attention. These methods utilise plant extracts, microorganisms, or biological derivatives as reducing and stabilising agents to extract nickel oxide from nickel salts.

• Processing in this way can reduce the use of hazardous reagents, decrease energy input and minimise waste and environmental toxicity, particularly in comparison to conventional chemical synthesis. Sustainable synthesis can be a more cost-effective processing method, and has feasibility for commercial scaling. The resulting NiO nanoparticles may offer enhanced biocompatibility and functionality for environmental and biomedical uses.

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Biomedical and Sensor Technologies

• Nickel oxide nanoparticles have shown promise in a number of biomedical and environmental applications, particularly within nickel oxide derived from sustainable synthesis.

• NiO nanoparticles are being explored for antimicrobial and antiviral performance, often enhanced under UV illumination via increased generation of reactive oxygen species. Its efficacy has been tested against a broad spectrum of bacteria and viruses, offering a drug-free approach to controlling a range of pathogens. This behaviour is being explored for use in wound dressings, disinfectants, and medical textile coatings, as well as preventing biofilm formation on medical devices.

• Early in vitro studies also report cytotoxic activity against certain cancer cell lines and parasites, highlighting their ability to disrupt cellular functions and trigger cell death, although much of this work remains in the preclinical phase.

• In diagnostics, NiO’s catalytic traits and rapid electron transfer support non enzymatic electrochemical biosensors (e.g. glucose or lactose detection), with potential durability and cost advantages over enzyme based systems. Similar approaches extend to environmental sensing of organic pollutants, or water and soil contaminants. Green synthesised nickel oxide has been investigated to identify and degrade dye pollutants, such as methyl red or methylene blue, within wastewater treatment, as well as heavy metal detection in agricultural soils.

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Advanced Nanostructures and Composites

• Fabricating nickel oxide in nanostructures, such as nanowires, nanosphere and nanoflowers, is essential for boosting material surface area and diffusion capabilities, ultimately increasing the reactivity and sensitivity of the sample product. Such architectures are particularly powerful for trace gas sensing. Further performance gains arise from composite designs, modification with noble metal nanoparticles, and surface functionalisation, improving both sensitivity and selectivity.

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Conclusion

Across industry and academia, nickel oxide is distinguished by its broad spectrum of advanced properties. Possessing a unique combination of chemical reactivity, thermal stability, semiconducting behaviour and tuneable surface chemistry has made it central to both traditional industries and emerging research areas.

This remarkably versatile compound enables progress from catalysis and metallurgy to energy technologies, sensors and smart coatings. Long established in batteries and fuel cell systems, NiO continues to contribute to higher efficiency and energy density in next generation devices. Within material fabrication, nickel oxide can play the part of a simple colourant, or can utilise its unique chemistry in areas such as electrochromic smart tech. Its versatility is highlighted by its ability to catalyse a wide range of reactions in many different environments. Meanwhile, the emergence of sustainable synthesis, biomedical exploration and high performance sensing technologies signal an evolving role for nickel oxide into new sectors.

As advanced nanotechnologies continue to develop, nickel oxide’s role is set to expand even further, positioning it as a key material in the transition toward cleaner energy, smarter devices, and greener industrial processes.

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Nickel Oxide at PI KEM

As research priorities evolve and production environments demand consistent reproducibility, sourcing nickel oxide optimised for the task is essential. PI-KEM supplies high quality green (NiO) and black (Ni₂O₃) nickel oxide powders from our partner Novamet Specialty Products, engineered to meet the precise standards of scientific and industrial users. Our portfolio spans multiple grades and particle size distributions, with options aligned to applications including ceramics and glass, catalytic systems, electrochemical devices and sensor development.

What sets PI-KEM apart is the combination of material quality and application insight. Dependable supply chains, rigorous quality assurance and source traceability ensure that every batch of nickel oxide meets specified standards for purity, particle size, stoichiometry, and performance, consistently delivering materials that meet the expectations of researchers and industrial users, minimising variability and supporting reliable experimental or production outcomes.

Our expert technical team can provide responsive, application-focused guidance to help you select the right grade for your method and scale. Whether you are developing a new catalyst, tuning an electrochromic film or building an SOFC/SOEC stack, our consistent, repeatable materials – and the years of expertise behind them – are designed to accelerate your path from experiment to outcome, driving progress across the materials science landscape.

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