Clean fuel: Sunlight to hydrogen with record efficiency

According to a study in Nature Communications, the device achieved a 20.8% solar-to-hydrogen conversion efficiency.
Image used for representational purposes only
Image used for representational purposes only

The Sun, a massive ball of hydrogen and helium held together by its own gravity, is the eternal source of light and solar energy, an unassailable component of life on this planet. But as major world powers deliberate on ways to adopt clean energy technology, hydrogen emerges as the winner, when consumed in a fuel cell, producing only water, electricity and heat. But an insuperable challenge is the production of hydrogen at a low cost.

Engineers of Rice University in Houston, US, have turned sunlight into hydrogen, exhibiting a record-breaking efficiency using a device that combines next-generation halide perovskite semiconductors with electrocatalysts in a single, durable, cost-effective and scalable device.

The lab of chemical and biomolecular engineer Aditya Mohite built the integrated photoreactor using an anti-corrosion barrier that insulates the semiconductor from water without impeding the transfer of electrons. According to a study in Nature Communications, the device achieved a 20.8% solar-to-hydrogen conversion efficiency.

The barrier, a bilayer, separates the desired functionalities that are attached to the photovoltaic component.
A system was designed that absorbs light and completes the water-splitting chemistry on its surface. A power source is connected to two electrodes for the electrolysis of water. But the researchers used a device known as a photoelectrochemical cell, where light is used as the energy source for electrolysis.

“Ours [device] is exceptional because it has record-breaking efficiency and the semiconductor is cheap,” said Austin Fehr, a chemical and biomolecular engineering doctoral student and one of the study’s lead authors. Their tests have shown that their barrier design worked for different reactions and semiconductors, making it suitable across several systems. The technology could transform hydrogen production, and how solar fuel is derived from fossil fuels.

Two layers of barriers were needed – one to block the water and another for good electrical contact between the perovskite and the protective layers. With hydrogen being used primarily in the refining and chemical sectors, and produced using fossil fuels such as coal and natural gas, it is thus responsible for significant annual carbon dioxide emissions. “Governments need to take rapid actions to lower the barriers holding low-carbon hydrogen back from faster growth,” Fatih Birol, IEA Executive Director, said.
Rice graduate students Ayush Agrawal and Faiz Mandani are the study’s lead authors alongside Fehr. Michael Wong, a Rice chemical engineer, is a co-author of the study.

Gas of future

  • First fleet of hydrogen fuel cell trains started operating in Germany in 2022
  • World’s first shipment of liquefied hydrogen from Australia to Japan in February 2022 was a key milestone in the international hydrogen market
  • Russia-Ukraine war pushed many govts, particularly Europe, to reduce dependency on fossil fuels, and look at low-emission hydrogen
  • Hydrogen demand in road transport has increased 60% since 2020
  • Ningxia Solar Hydrogen Project is world’s largest electrolyser in operation
  • (Source: IEA Global Hydrogen Review, 2022)

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