How Nickel Compares to Other Metals in Catalytic Converters

Catalytic converters are most often associated with platinum, palladium, and rhodium, the three platinum group metals (PGMs) responsible for the chemical reactions that reduce harmful vehicle emissions.

These precious metals play a central role in transforming dangerous pollutants produced by the internal combustion engine into less harmful compounds before they exit a vehicle’s exhaust system.

Automotive catalytic converters are far more complex than a simple collection of precious metals. A typical converter contains a carefully engineered combination of materials designed to withstand extreme high temperatures, maximize surface area, and support efficient catalysis. These materials include ceramic substrates, stabilizing oxides, specialized washcoat layers, and several supporting base metals, including nickel.

Nickel is not considered a primary catalytic metal in modern automotive catalyst technology. Instead, it can appear in supporting roles in the overall emissioncontrol system. In some cases, it contributes to the structural integrity of the substrate, while in others it may be incorporated into alloys or experimental catalyst materials under research in the automotive industry.

Understanding the full composition of catalytic converters is valuable for recyclers, refiners, and industry professionals who analyze converters for processing and recovery. That’s why we’re giving you the full guide on nickel!

What materials are used in catalytic converters?

Before we jump into the all-inclusive guide to nickel, it’s important to understand how a converter works. More specifically, how the materials coexist and work with each other.

Modern automotive catalytic converters rely on a layered system of materials that work together to convert harmful engine exhaust into less damaging gases. Each component plays a specific role in the chemical reactions that reduce air pollution and help vehicles meet strict emission standards and emission regulations set by organizations like the EPA.

Substrate (ceramic or metallic)

At the core of most catalytic converters is the substrate, which provides the structural foundation for the catalyst system.

Most converters use a ceramic substrate made from cordierite. This material is molded into a honeycomb structure containing hundreds of small channels that allow exhaust gas to flow through while maximizing surface area. The honeycomb design ensures that the catalytic materials can interact with as much engine exhaust as possible.

Some heavy-duty applications or specialized converters use metallic substrates made from heat-resistant alloys. These materials can tolerate rapid temperature fluctuations and are sometimes used in systems exposed to extremely high exhaust emissions temperatures, like certain diesel engines.

Washcoat layer

The substrate is coated with a porous layer called the washcoat, which dramatically increases the surface area available for catalytic activity.

The washcoat typically contains several oxides, including:

• Aluminum oxide (alumina)
• Cerium oxide
• Zirconium oxide
• Additional compounds used for stabilization

These materials create a rough, high-surface-area texture that allows precious metals to disperse evenly across the substrate. The increased surface area is essential for efficient catalysis, allowing more exhaust gas molecules to interact with the catalyst material during operation.

Precious metal catalysts

The active catalysts responsible for reducing harmful vehicle emission compounds are the platinum group metals:

• Platinum
• Palladium
• Rhodium

Each metal performs a specific function in automotive catalytic converters.

Platinum and palladium act primarily as oxidation catalysts, helping convert carbon monoxide and hydrocarbons into carbon dioxide and water. Rhodium, on the other hand, functions as a reduction catalyst, breaking down nitrogen oxides (NOx) into nitrogen and oxygen.

Together, these reactions reduce many of the most harmful toxic substances produced by internal combustion engines.

Base metals and additives

In addition to precious metals, catalytic converters may include smaller amounts of base metals and stabilizers that improve catalyst performance and longevity.

Examples include:

• Nickel
• Iron
• Lanthanum
• Cerium

These materials help improve the durability and thermal stability of the catalyst system. While they typically do not drive the main catalytic reactions, they support the structure and stability of the catalyst material, especially during repeated exposure to high temperatures in the vehicle exhaust stream.

Why are precious metals used in catalytic converters?

The use of precious metals (primarily PGMs) in catalytic converters is not accidental. These metals possess unique chemical properties that allow them to catalyze reactions efficiently under the extreme conditions found inside an exhaust system.

One of the key reasons for using platinum group metals is their exceptional catalytic efficiency. These metals accelerate the chemical reactions that convert harmful pollutants into less harmful gases without being consumed in the process.

They also offer remarkable resistance to the high temperatures generated by engine exhaust. During normal operation, converters may experience temperatures exceeding 800°C, particularly under heavy engine load or when addressing cold-start conditions. PGMs maintain their catalytic activity even under these demanding conditions.

Chemical stability is another critical factor. Platinum, palladium, and rhodium resist corrosion and oxidation better than many other metals, allowing them to function effectively throughout the life of the converter.

Durability is especially important because catalytic converters must continue functioning for tens of thousands of miles while meeting strict emission standards.

While PGMs drive the core catalytic reactions responsible for emission control, supporting materials, including nickel, may still play smaller roles within the catalyst system.

Is nickel used in catalytic converters?

The short answer is yes, nickel can be used in catalytic converters, but it’s not a primary catalyst in modern automotive catalytic converters.

Instead, nickel typically appears in supporting or experimental roles within catalyst systems. Let’s take a look at these roles.

Catalyst research and alternative systems

Nickel is a known catalytic metal that has been used in industrial chemical processes for decades. It can catalyze reactions such as hydrogenation, reforming, and methane reforming, making it valuable in chemical manufacturing and hydrogen production.

Because nickel is far less expensive than platinum group metals, researchers sometimes explore nickel-based catalysts as potential alternatives. These investigations aim to reduce reliance on expensive PGMs while maintaining efficient emission control.

However, nickel generally performs less reliably in the harsh environment of an automotive exhaust system.

Washcoat additives

In some catalyst formulations, nickel compounds may be incorporated into the washcoat layer alongside other oxides. In these cases, nickel may help stabilize the structure of the catalyst or influence certain oxidation reactions.

These roles are typically supportive rather than primary, and explain why you won’t find nickel in your assay report.

Metallic substrate alloys

Nickel can also appear as part of heat-resistant alloys used in metallic substrates. These alloys help ensure that the honeycomb structure remains stable even when exposed to repeated cycles of heating and cooling within the vehicle exhaust stream.

Industrial and experimental catalysts

Outside the automotive industry, nickel catalysts are widely used in industrial reactors, hydrogen production systems, and chemical processing facilities. They may also appear in experimental automotive catalyst research aimed at reducing the cost of emissioncontrol systems.

Even so, modern catalytic converters still rely primarily on platinum, palladium, and rhodium due to their superior performance and reliability.

Nickel’s chemical and physical properties

Several properties make nickel attractive for catalyst research and alloy design.

Nickel demonstrates catalytic activity in reactions involving hydrogenation, reforming, and oxidation. These reactions are widely used in industrial catalysis and chemical manufacturing.

The metal also has a high melting point of approximately 1455°C, which gives it good resistance to heat. This makes nickel-containing alloys useful in components exposed to extreme engine exhaust temperatures.

Nickel is also significantly less expensive than platinum group metals, making it appealing for researchers investigating alternative catalyst materials.

Another advantage is nickel’s ability to improve the mechanical strength and corrosion resistance of metal alloys. When added to steel or other metals, it enhances resistance to oxidation and structural degradation.

These characteristics don’t make nickel valuable to vehicle engine catalysis, but they do make it particularly interesting in the design of heat-resistant alloys used in some automotive catalyst components.

How does the nickel coating process on substrates affect emissions?

Nickel coatings are not a standard feature of all catalytic converters, but certain catalyst designs may incorporate nickel compounds within the coating process.

The manufacturing process generally begins with preparing the ceramic substrate or metallic substrate to receive catalytic coatings.

Next, the washcoat is applied as a slurry containing materials such as aluminum oxide, cerium oxide, and other stabilizing oxides. This coating forms a highly porous layer with large surface area, allowing catalytic metals to interact efficiently with exhaust gas.

After the washcoat is applied, the precious metal catalysts, typically platinum, palladium, and rhodium, are deposited onto the surface.

Potential nickel roles

When used, nickel compounds may be incorporated into this coating system to enhance adhesion between layers, influence oxidation reactions, or stabilize the catalyst structure at very high temperatures.

Impact on emissions

If integrated effectively, nickel may help maintain the structural integrity of the catalyst under demanding operating conditions. This stability can support the long-term performance of the converter as it processes vehicle exhaust.

However, nickel alone cannot achieve the level of emission control required by modern emission regulations. The catalytic reactions necessary to reduce carbon monoxide, hydrocarbons, and nitrogen oxides still depend primarily on platinum group metals.

Why you won’t find nickel on your assay report

For those involved in catalytic converter recycling, nickel rarely appears on an assay report.

The reason is simple: nickel is not the primary catalyst material responsible for reducing exhaust emissions.

Nickel catalysts are more susceptible to deactivation than PGMs. They can be poisoned by sulfur compounds, carbon deposits, and other contaminants present in engine exhaust.

Nickel is also more prone to oxidation at the temperatures encountered in automotive exhaust systems, which can degrade its catalytic effectiveness over time.

Additionally, nickel typically provides lower catalytic efficiency than platinum, palladium, or rhodium when it comes to reducing nitrogen oxides, oxidizing carbon monoxide, or converting hydrocarbons.

Because converters must withstand extreme conditions, like constant exposure to heat, vibration, and corrosive gases, PGMs remain the preferred catalysts for long-term durability.

For recyclers, this means the economic value of a catalytic converter comes almost entirely from the recoverable platinum group metals. Nickel, if present, usually remains part of base metal streams during refining and does not significantly influence converter pricing.

Still, understanding these materials can help you better interpret converter composition and anticipate future changes in automotive catalyst technology.

A look to the future: could nickel play a larger role in emissions catalysts?

Researchers continue to explore ways to reduce reliance on expensive precious metals in emissioncontrol systems. Nickel-based catalysts are one of several areas of ongoing research.

Some studies focus on hybrid catalyst systems that combine nickel with advanced oxides or other materials to improve catalytic activity while reducing the amount of platinum group metals required.

At the same time, evolving technologies in the automotive industry (hybrid vehicles, advanced diesel engine aftertreatment systems, and even fuel cell technologies) may influence how catalysts are designed in the future.

Diesel vehicles, for example, often use additional components such as a particulate filter to capture particulate matter, while gasoline vehicles continue to rely heavily on three-way catalysts for emission control.

Despite these developments, modern automotive catalytic converters still depend primarily on platinum, palladium, and rhodium to meet strict global emission standards designed to reduce air pollution.

Nickel can appear in catalytic converter systems, but it doesn’t function as the primary catalytic metal responsible for reducing vehicle emissions. Instead, its role is generally supportive, helping improve the durability, stability, or structural performance of certain catalyst components.

The metals that drive the key chemical reactions responsible for reducing pollutants in vehicle exhaust remain the platinum group metals: platinum, palladium, and rhodium.

These metals enable catalytic converters to transform harmful gases such as carbon monoxide, hydrocarbons, and nitrogen oxides into less harmful by-products like carbon dioxide, nitrogen, and water.

For recyclers and industry professionals, understanding how these materials interact within automotive catalytic converters provides valuable insight into converter design, emissioncontrol systems, and the economic value of recovered PGMs.

Discover the roles of platinum group metals in catalytic converters. Contact one of our experts now!