Nickel catalysts: the many routes to decarbonising transport

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Nickel-based catalysts are key to supplying energy to power our transportation of goods and people, whether by land, sea, or air. In addition to their role in the production of biodiesel, renewable diesel and SAF (sustainable aviation fuel), nickel catalysts are used for water electrolysers for hydrogen production. Hydrogen can then be burned directly, used in fuel cells, used to hydrotreat other renewable fuels, or be converted to another fuel such as methanol or ammonia. Hydrogen can also be used in the net-zero production of other chemicals, or for production of steel from iron ore.

By Steve Deutsch, The Catalyst Group, for Nickel Institute

Electroysers and fuel cells

Electrolysers split water into oxygen and hydrogen. A fuel cell is an electrolyser in reverse, combining oxygen and hydrogen into water to produce electricity. When produced using renewable energy, this is called “green” hydrogen, and the International Energy Agency predicts that demand for it will explode over the next 25 years.
There are four types of electrolysers available today: polymer electrolyte membrane (also known as proton-exchange membrane, PEM), alkaline water electrolyser (AWE), anion exchange membrane (AEM), and solid-oxide electrolyser cell (SOEC). While PEM electrolysers are the most efficient, they require the use of platinum and iridium as electrocatalysts, while the other three technologies use nickel-based electrocatalysts. Of the nickel-containing types, AWEs are the most commercially advanced. In AWEs, nickel is found in the anode, the cathode, and in the flow field components of the electrolyser cell. The flow field consists of a loose nickel mesh, to allow for easy transport of electrolyte and evolved gases. The anode is typically an engineered nickel mesh consisting of sintered fibres, while the cathode is a similar nickel fibre mesh coated with a catalyst. These catalysts are proprietary to the supplier, but NiFeOx is commonly used.

AEM Anion exchange membrane
AWE Alkaline Water Electrolyser
PEM Polymer electrolyte membrane/Proton exchange membran
SOEC SDolid-oxide electrolyser cell

Pros and cons of different catalysts

Expanded view of AWE cellIn AWEs, nickel is found in the anode, the cathode, and in the flow field components of the electrolyser cell. ©Copyright 2016 Industrie De Nora S.P.A.
Expanded view of AWE cell
In AWEs, nickel is found in the anode, the cathode, and in the flow field components of the electrolyser cell. ©Copyright 2016 Industrie De Nora S.P.A.

The relatively low capital cost of AWEs has led to their increasing use, but in order to minimise production costs and meet the demand for renewable electricity, AEMs and SOECs are being introduced. AEMs have the benefit of higher electrical efficiency compared to AWEs, while using similar materials, and so are often thought of as an intermediate between AWEs and PEMs. Like AWEs, AEMs use nickel meshes to control flow and to deliver current, and also use nickel catalysts. In contrast to the relatively simple catalysts used in AWEs, AEM catalysts tend to be more highly engineered. Proposed anode catalysts showing high performance include NiFe double layered hydroxides supported on carbon paper and NiCoSe alloys supported on Ni foam. Cathode catalysts tend to be NiFe and NiCo alloys supported on Ni mesh.
SOECs operate at very high temperatures (>600 °C) and offer high efficiency with the ability to integrate waste heat into industrial applications. In SOECs, the electrocatalyst, often Ni metal particles, is supported directly on the electrolyte, which is a metal oxide that becomes conductive to ions at the high operating temperature.

Irreplaceable nickel

These are just examples of the role that catalysts and other components using nickel will play in a decarbonised future. Nickel’s relatively low cost, inertness to caustic substances, and specific performance features in electrolysers make it an irreplaceable part of these emerging technologies.

About Nickel Institute

The Nickel Institute is the global association of leading primary nickel producers. Its mission is to advocate for the responsible supply and sustainable development of nickel and the nickel industry. For information, visit nickelinstitute.org

About this Tech Article

This tech article appeared in Stainless Steel World, January/February 2024 magazine. To read many more articles like these on an (almost) monthly basis, subscribe to our magazine (available in print and digital format) – SUBSCRIPTIONS TO OUR DIGITAL VERSION ARE NOW FREE.

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