Hydrogen-burning internal combustion engines present a promising solution in the fight against climate change. These engines provide a powerful, carbon-free alternative to traditional fuels, making them ideal for heavy-duty trucks, buses, off-road equipment, and agricultural machinery. In addition, they are useful for backup power generation, offering cleaner energy solutions compared to diesel engines.
Although hydrogen engines do not emit earth-warming carbon, they are not entirely free of pollutants. During high-temperature combustion, they produce nitrogen oxides (NOx), which react with atmospheric compounds to form ozone and fine particulate matter. These pollutants can aggravate respiratory conditions and lead to long-term health problems. This makes reducing nitrogen oxide emissions critical in improving the environmental performance of hydrogen engines.
Scientists at the University of California, Riverside (UCR) have developed a cost-effective solution to significantly lower the pollution produced by hydrogen engines. Their research focuses on enhancing the efficiency of catalytic converters, key components in emission control systems.
In a study published in Nature Communications, UCR researchers discovered that infusing platinum in catalytic converters with a highly porous material known as Y zeolites dramatically increases the conversion of nitrogen oxides into harmless nitrogen gas and water vapor. This breakthrough was achieved by promoting better reactions between nitrogen oxides and hydrogen inside the converter.
Y zeolites, a synthetic form of the zeolite family, are low-cost materials made primarily from silicon, aluminum, and oxygen atoms. Their crystalline structure features a large surface area with uniform pores and channels that promote efficient pollutant breakdown. When platinum is mixed with Y zeolites, the material forms a water-rich environment during hydrogen combustion. This environment enhances the activation of hydrogen, which plays a critical role in boosting nitrogen oxide reduction.
Compared to traditional catalytic converters, the new design demonstrated a four- to five-fold increase in nitrogen oxide conversion at 250 degrees Celsius. The system was particularly effective at lower temperatures, making it highly beneficial in reducing emissions during engine start-up when temperatures are still relatively low.
Beyond hydrogen engines, the catalytic converter design may also reduce emissions from diesel engines fitted with hydrogen injection systems. This method is similar to the selective catalytic reduction systems currently used in large diesel trucks to control nitrogen oxide emissions. The integration of hydrogen into these systems offers further potential to decrease the environmental impact of diesel-powered machinery.
The UCR team, led by Fudong Liu, an associate professor of chemical and environmental engineering, sees this advancement as a critical step toward cleaner, more sustainable combustion technologies. With the addition of low-cost Y zeolites to catalytic converters, hydrogen engines can move closer to being an effective, low-emission alternative for heavy-duty and industrial applications.
