In the 1800s, British scientists passed an electric current through water, then watched it bubble and fizz as it separated into its component elements: hydrogen and oxygen. Today, this process—known as water splitting—is regarded as a promising eco-friendly way to generate clean hydrogen, free from heavy carbon emissions.
Water splitting relies on renewable energy in electrochemical cells, where catalysts help break water into hydrogen and oxygen. The resulting hydrogen can then be used as a clean fuel, with water as the only byproduct.
“Catalysts play a key role by lowering the energy required for the water-splitting process and speeding it up,” said Lili Zhang, Division Director at A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE2). “However, many of today’s water-splitting catalysts are not fully efficient, leading to scalability and cost issues.”
In partnership with researchers at Shihezi University, China, Zhang and colleagues set out to create a more efficient, scalable and cost-effective catalyst for water splitting reactions. By introducing silicon (Si) into nanosheets made from ZnAl-layered double hydroxide (ZnAl-LDH), the team aimed to improve the catalyst's performance with the help of sunlight.
Nanosheets are ideal for hydrogen catalysts because their two-dimensional layered structure improves light absorption, enhances the separation and transfer of photoexcited carriers, and increases the number of active catalytic sites present, making them highly efficient at water splitting compared to traditional materials.
“By harnessing light energy, we can reduce the amount of electricity needed, making the process more energy-efficient and potentially lowering costs,” Zhang noted.
To achieve this, the team made Si-doped ZnAl-LDH nanosheets through a process called chemical exfoliation, which allowed them to peel off ultrathin layers. "These layers expose more useful surface areas that can enhance processes like water splitting," Zhang explained.
The team then tested their material under light using a three-electrode system, with exciting results: adding silicon improved the movement of charges and increased reaction sites, lowering the energy needed for the catalyst to split water and boosting its performance beyond that of standard catalysts.
“Our study introduces an affordable and efficient photoelectric catalyst for green hydrogen production by combining sunlight and electricity to reduce energy consumption, costs and material wear,” said Zhang. The team is now refining their nanosheet’s structure to further boost its efficiency and scalability.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE2).
