Artificial leaf. (Image Credit: University of Cambridge)
The green hydrogen market has become a big hit due to affordable solar and wind power for water electrolysis. Researchers are working on replicating nature’s photosynthesis process. The artificial leaf has finally started taking shape as we set our sights on more renewable energy systems. University of Cambridge researchers are marketing an affordable, durable artificial leaf that floats atop water to generate electricity, an alternative to solar arrays taking up land space.
An artificial leaf is created through a very simple process. First, scientists fabricate a photoelectrochemical cell before dipping it in a water-based solution. Afterward, it undergoes light exposure to replicate the same chemical reaction found in photosynthesis. Photoelectrochemical cells have two subsets, but only one can be used for solar-to-hydrogen generation. Some may even ask why we use photoelectrochemical systems to create green hydrogen if water electrolytes can do the job.
According to artificial leaf researchers, the efficiency of an electrolysis system and the green inputs outperforms solar cell energy production. Last year, Purdue researcher Yulia Pushkar said that artificial photosynthesis does not have any “fundamental physical limitations.” She explained, “You can very easily imagine a system that is 60% efficient because we already have a precedent in natural photosynthesis. And if we get very ambitious, we could even envision a system of up to 80% efficiency.”
Contrarily, solar cells have an average solar conversion efficiency of approximately 20%, and even specialized types can achieve higher rates. However, those are more costly than those deployed today. Photoelectrochemical hydrogen systems still need work before hitting the market. Scientists can replicate the photosynthesis chemical reactions, but it’s not durable enough.
Semiconductors in photoelectrochemical cells undergo corrosion whenever it’s submerged in a water-based solution. The Energy Department even says this durability issue can be solved. “PEC [photoelectrochemical] water splitting is a promising solar-to-hydrogen pathway, offering the potential for high conversion efficiency at low operating temperatures using cost-effective thin-film and/or particle semiconductor materials,” it explains, while stating “continued improvements in efficiency, durability, and cost are still needed for market viability.”
The agency thought of a set of best practices created by the Lawrence Berkeley National Laboratory and the National Renewable Energy Laboratory. “The article spells out the path so that all laboratories can follow a uniformity of experimental practices, beginning with the materials needed for the fabrication of photoelectrodes,” NREL explained.
NREL achieved a 12.4% solar-to-hydrogen efficiency record, but that number was brought down in 2016 because the lab determined the experiment had been over-illuminated. In 2017, the NREL achieved a 16.2% solar-to-hydrogen conversion efficiency, setting a new record. The Energy Department wants to hit 25% efficiency, but NREL says that these systems could be competitive without reaching that target.
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