A scanning electron microscope image of 'coral-like' barium titanate nanoparticles. Credit: Nature Communications, City University of Hong Kong

Converting temperature fluctuations into clean energy 

11 January 2023

Pyro-catalysis has attracted increasing attention, because it is a green, self-powered catalysis technique, which harvests waste thermal energy from the environment. Researchers have made advances towards a significantly faster and more efficient pyro-catalytic reaction than ever before, possibly overcoming the drawbacks which previously hindered its practical application.

Pyroelectric catalysis can convert environmental temperature fluctuations into clean chemical energy, like hydrogen. Compared with photocatalysis, however, pyro-catalysis is inefficient due to slow temperature changes in the ambient environment. A team co-led by Dr Lei Dangyuan and researchers at City University of Hong Kong has found a way towards greater speed and efficiency by using localised plasmonic sources to heat up the pyro-catalytic material and to allow it to cool down. Their findings open up new avenues for efficient catalysis for biological applications, pollutant treatment and clean energy production.

The efficiency of most currently available pyroelectric materials rely on the change of ambient temperature over the time. As this change rate is often limited, a more viable way to increase the pyro-catalytic efficiency is to increase the number of temperature cycling. But it is a great challenge to achieve multiple thermal cycling in the pyro-catalyst within a short time interval using conventional heating methods. The team overcame this obstacle using a novel strategy of combining pyroelectric materials and the localized thermo-plasmonic effect of noble metal nanomaterials.

The plasmonic nanostructures, which support the collective oscillation of free electrons, can absorb light and convert it quickly into heat. Its nanoscale size allows fast yet effective temperature changes within a confined volume, without significant heat loss to the surrounding environment. Consequently, the generated localised heat can be easily fine-tuned and turned on or off by external light irradiation within an ultrashort interval of time.

In their experiments, the team used barium titanate nanoparticles containing gold nanoparticles as plasmonic heat sources, which can convert the photons directly from a pulsed laser to heat. The experiment demonstrated that gold nanoparticles act as a rapid , dynamic and controllable localized heat source without raising the surrounding temperature, which efficiently boost the overall pyro-catalytic reaction rate of barium titanate nanoparticles.

The team achieved a high pyro-catalytic hydrogen production rate, speeding up the practical application development of pyro-catalysis. The results also suggest that performance could be improved in the future by increasing the laser pulse repetition rate.

The research team believes they have opened up a new approach by designing an innovative pyroelectric composite system with other photothermal materials. Further improvements may see future applications of pyro-catalysis in pollutant treatment and clean energy production.

The findings were published in the journal Nature Communications