Hydrogen vehicles get cleaner with pollutant scrubber

Hydrogen vehicles emit no carbon: their combustion engines rely on H₂ alone. This has made them a promising option for zero-emissions heavy vehicles.

But, like petrol cars, current hydrogen engines can still emit polluting compounds called nitrogen oxides.

A team in the US has figured out a way to stop hydrogen engines from releasing these gases, rendering them even cleaner.

They’ve published their discovery in Nature Communications.

The method involves infusing platinum with a type of material called Y-zeolite, and adding it to the catalytic converter of an internal combustion engine.

Zeolites are low-cost crystalline materials, with lots of pores and a cage-like crystal structure that makes them useful as tiny sieves or sponges in chemistry.

This zeolite was made using yttrium and titanium. The researchers mixed it with platinum and tested its behaviour in a hydrogen combustion reaction.

Hydrogen combustion works by reacting hydrogen (H₂) with oxygen (O₂) in the air, and generating water (H₂O) and energy.

In a hydrogen engine, this reaction can also form nitrogen oxide by-products (NO_x), thanks to the nitrogen (N₂) in the air.

The team found that the zeolite/platinum mixture was very good at “reducing” these nitrogen oxides: it prompted them to react back into nitrogen and water.

The platinum catalysed the reaction, and the zeolites helped it along by retaining water.

“We don’t need to use complicated chemical or other physical processes,” says co-author Liping Liu, a PhD student at Virginia Polytechnic Institute and State University, USA.

“We just mix the two materials – platinum and zeolite – together, run the reaction, and then we see the improvement in activity and selectivity.”

Alongside being easy to do, the researchers say that their compound is sustainable to manufacture requiring just mixing powders together at low temperatures.

“We’ve developed a new technology to deal with nitrogen oxide emission control, and we think it’s an amazing technique,” says first author Dr Shaohua Xie, a research scientist at the University of California – Riverside, USA.