Water-splitting panel makes hydrogen more efficiently
A solar panel that can split water into hydrogen and oxygen 10x more efficiently than previous artificial photosynthesis schemes has been developed by researchers at the University of Michigan.
The catalyst is made of indium gallium nitride nanowires grown on a silicon surface, which bring the benefit of being able to handle much higher temperatures than previous systems. The elevated temperatures in turn speed up the synthesis process and inhibit recombination of the hydrogen and oxygen.
The panel has achieved a 9 percent efficiency in converting water into hydrogen and oxygen. Such artificial photosynthesis is one of the most promising pathways to sustainable hydrogen as an energy supply.
The team makes use of a lens about the size of a house window to focus light down on to panel a few inches across containing the semiconductor chip under water.
“We reduced the size of the semiconductor by more than 100 times compared to some semiconductors only working at low light intensity,” said Peng Zhou, University of Michigan research fellow in electrical and computer engineering and first-named author of the study.
An insulating layer keeps the panel at 75 degrees C, a good compromise for the splitting process and long-term use of the semiconductor. The outdoor version of the experiment, with less reliable sunlight and variable temperature, achieved 6.1 percent efficiency at turning the energy from the sun into hydrogen fuel. However, in a controlled environment indoors, the system achieved 9 percent efficiency.
Next the team intends to further improve the efficiency of the synthesis and to achieve high purity hydrogen that can be directly fed into fuel cells.
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