Zero-dimensional transistor harvests bubble energy wasted during water electrolysis

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Posted on August 14, 2013
A zero-dimensional transistor is placed in contact with a water droplet containing NaCl ions. A current between the anode and cathode generates hydrogen and chlorine bubbles, which the transistor can detect and transform into electric pulses. Credit: N. Clément, et al. ©2013 American Chemical Society

A zero-dimensional transistor is placed in contact with a water droplet containing NaCl ions. A current between the anode and cathode generates hydrogen and chlorine bubbles, which the transistor can detect and transform into electric pulses. Credit: N. Clément, et al. ©2013 American Chemical Society

When hydrogen is produced from water during electrolysis, some energy is lost as tiny bubbles. In a new study, researchers have demonstrated that 25-nm transistors—so small that they’re considered zero-dimensional (0D)—can be used to transform this lost energy into electric pulses. Millions of these 0D transistors could be used to detect individual bubbles and generate electric pulses at an optimal efficiency, gathering part of the energy lost during electrolysis and making it available for other uses.

The researchers, Nicolas Clément at CNRS in Villeneuve d’Ascq, France, and his coauthors, have published their paper on using 0D transistors to harvest energy from bubbles in a recent issue of Nano Letters.

As one of the most promising approaches for producing hydrogen as a fuel source, electrolysis involves applying an electric current to water to separate the oxygen andhydrogen atoms. During electrolysis, gas bubbles are formed, causing some energy loss.

“All the mechanisms of energy loss during electrolysis are not fully understood,” Clément told Phys.org. “Such a device, combined with high-precision cameras, may improve understanding in the future. Sources of energy loss are either diffusion of hydrogen in water or movement of counterions around electrodes during bubble emission.”

To demonstrate how 0D transistors can recover some of this energy, the researchers placed a 0.2-microliter droplet of salt water in a microbath. Underneath, they placed a transistor and two electrodes. Under an applied voltage, relatively small (18-24-?m) hydrogen bubbles were emitted at the cathode, while larger chlorine bubbles were emitted at the anode. Increasing the voltage resulted in an increase in the bubble emission frequency.

 

Read more at: Phys.org