The drive for countries to meet goals set by the Paris Agreement, as well as the European Green Deal and REPowerEU plan of keeping global warming to below 1.5 degrees Celsius has meant that emissions of greenhouse gases must be reduced by 45% by 2030 and must reach net zero by 2050.
To do this, alternative renewable energy sources must replace the burning of fossil fuels, which release greenhouse gases and is thus a major contributor to human-driven climate change.
Solar energy has become a major player in renewable energy plans, taking light from the Sun and converting it directly into electricity. However, there is another way to use light from the Sun to generate clean energy.
The case for photocatalysis
Taking its inspiration from plants and other organisms that convert sunlight to chemical energy during a process called photosynthesis, photocatalysis uses sunlight as an activation energy source to drive chemical conversions, namely the artificial splitting of water to create hydrogen. This hydrogen could potentially replace natural gases as a fuel source, thus reducing the emission of greenhouse gases and atmospheric carbon, making the goal of net zero by 2050 more than an unachievable dream.
A new paper published in the journal Global Challenges looks at three photocatalyst case studies with different scales: from a laboratory test, through an outdoor pilot scheme, to a large industrial plant-sized panel system.
“Photocatalysis is a promising solution for renewable energy generation because it simply uses light and catalysts to convert the most abundant renewable energy source, solar energy, into chemical energy,” said the paper’s corresponding author Pablo Jiménez Calvo, a post doctoral researcher at the Max Planck Institute of Colloids and Interfaces. “This method is clean, efficient, and sustainable.”
He added that photocatalytic reactions can produce fuels, such as hydrogen or alcohols, or chemical products, like fine chemicals, pharmaceuticals, and agrochemicals. But, to provide enough energy to meet the burden of fossil fuels, the process must overcome significant challenges including scalability, efficiency, and cost.
Will it make it to large-scale production?
Jiménez-Calvo explained that the focus of the studies examined in the paper was transferring technology to produce hydrogen on a larger scale. “Photocatalysis has a number of challenges that need to be addressed, such as low photocatalytic activity, issues with band gap energy, fast recombination of photo-generated electrons and holes, stability problems, poor light utilization, and cost,” said.
“These factors limit the efficiency of photocatalysts and their practical applications,” he continued. “Overcoming them requires rethinking current tendencies, concepts, and methods to enhance the technology’s activity.”
Jiménez-Calvo detailed the results of the three studies and their potential impact on the large-scale adoption of artificial water splitting. “On the laboratory scale, a compact reactor was designed with improved engineering features,” he said. “This led to increased rates of photoproduction of hydrogen compared to earlier studies. The increase is likely due to reduced process losses, such as enhanced light absorption in photonics, as evidenced by superior quantum yields.”
The pilot device was tested in an outdoor setting, which showed that photocatalyst technology can be effectively transferred to real-world conditions.
“Finally, Japanese scientists designed a large panel system that achieved a similar solar-to-hydrogen conversion rate as the lab scale, despite being located outdoors and producing much more hydrogen,” Dr. Jiménez-Calvo added. “This project represents a major proof-of-conceptin the field of photocatalytic science.”
The three studies demonstrated latest technological progress occurring at different scales. “Because photocatalysis has moved beyond the laboratory and pilot stages, as proven by successful panel array plant installations, this evidence supports the potential for further investment and scaling up of photocatalysis technology,” continued Jiménez-Calvo.
In addition to its use as a source of green renewable energy, photocatalysis is also versatile, having applications in the water and air purification field, potentially providing energy-storage materials in the form of superconducting materials raised from their ground energy state by sunlight.
“Photocatalysis has the potential to be a game-changer in the energy sector. With critical strategies and smart technological implementations, photocatalysis can foster its technological readiness level and become a feasible, efficient, clean, and sustainable energy solution for the future,” Jiménez-Calvo concluded.
Reference: M. Isaacs., J. Garcia-Navarro., W-J. Ong., P. Jiménez-Calvo, Is Photocatalysis the Next Technology to Produce Green Hydrogen to Enable the Net Zero Emissions Goal?, Global Challenges (2023). DOI: 10.1002/gch2.202200165
Feature image credit: Masaaki Komori on Unsplash