The aim of this project is to develop efficient low-temperature H₂-deNO_x catalysts for the exhaust gas of lean H₂ direct injection (H₂-DI) combustion engines, including trucks, heavy-duty vehicles, ships, and stationary applications, particularly CHP units. These engines eliminate CO₂ emissions and are therefore considered a promising solution for decarbonising transport and energy systems. However, they are not yet commercially available because they still produce nitrogen oxides (NO_x), making effective exhaust gas aftertreatment essential for meeting regulatory requirements and enabling market entry.
Conventional selective catalytic reduction (SCR) remains the state-of-the-art deNO_x aftertreatment technology for exhaust gas temperatures above 220 °C. However, SCR exhibits limited efficiency below 220°C—conditions encountered during cold starts, city driving, and low-load stationary operation. To address this gap, we will develop a novel catalytic approach that uses H₂ as the reducing agent for low-temperature NO_x abatement (80 – 220°C). The hydrogen required for this process is supplied directly from the vehicle's existing fuel tank, eliminating the need for additional infrastructure or reductant storage systems, such as urea in conventional SCR.
However, the H₂-deNO_x reaction faces two key challenges despite its high efficiency in lean H₂ combustion exhaust gas: N₂O secondary emissions and over-stoichiometric H₂ consumption. The relevant reaction pathways include:

            2 NO(g) + 2 H₂(g) → N₂(g) + 2 H₂O(g)       ∆H⁰ = -668 kJ/mol

            2 NO(g) + H₂(g) → N₂O(g) + H₂O(g)          ∆H⁰ = -342 kJ/mol

            O₂(g) + 2 H₂(g) → 2 H₂O(g)                       ∆H⁰ = -572 kJ/mol

To maximise N₂ selectivity while minimising N₂O formation and H₂ consumption by O₂, the improvement and design of the low-temperature H₂-deNO_x catalyst will be achieved through screening various powder catalyst formulations, which will be evaluated for NO_x conversion using synthetic exhaust gas.
The most efficient catalyst will be selected and assessed based on the following criteria:

• NO_x conversion > 80% between approx. 80 and 220°C
• Selective conversion of NOₓ into N₂ (no N₂O or NH₃ emissions)
• H₂ selectivity toward NO_x > 50% to suppress competing H₂ consumption by O₂
• Hydrothermal stability

This selected powder catalyst will be coated onto cordierite monolith cores for laboratory reactor experiments and engine test bench trials.
In parallel with experimental catalyst development and testing, a comprehensive microkinetic model will be developed to elucidate the fundamental catalytic chemistry governing H₂-deNOₓ performance. The predictive model will consist of H₂ oxidation, NO reduction, N₂O, NO₂, and NH₃ formation, as well as NH₃ oxidation sub-mechanisms. This model will provide valuable insights into the behaviour of H₂-deNO_x reactivity across various conditions and will support the continued development of predictive models.
In conclusion, these findings will lay the groundwork for advancing exhaust aftertreatment technologies for H₂-DI combustion engines and will aid industry partners in developing efficient, cost-effective emission reduction solutions. Amid increasingly stringent emission regulations, this work will open new market opportunities and support the commercial deployment of lean H₂-DI combustion engines during the ongoing energy transition.

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