Artificial leaves goal for New Zealand-China greenhouse gas project

New Zealand and Chinese researchers are endeavoring to create a synthetic leaf to use or consume the greenhouse gas, carbon dioxide (CO2).

University of Canterbury (UC) researchers said Wednesday they had teamed up with the City University of Hong Kong in a project to learn from nature and use photosynthesis in natural green leaves as the blueprint to develop a "sunlight-driven" process to turn CO2 into fuel or other products.

The project, titled "Decorating Artificial TiO2 leaves for Effective Carbon Dioxide Capture and Usage," aimed to deal with climate change, the planet's biggest threat, said Dr Alex Yip, of UC's Chemical and Process Engineering department.

"The United Nations climate summit in Paris, in December 2015, set a target of limiting global warming to below 2 degrees Celsius above pre-industrial times. We believe chemical processes that capture and convert waste CO2 into useful chemicals are viable pathways to cut CO2 emissions," Yip said in a statement.

The New Zealand team had already replicated the key structures in natural leaves that were responsible for light-harvesting and photosynthesis using titanium dioxide (TiO2), a proven photocatalyst for CO2 reduction.

An important approach for converting waste CO2 into useful fuels and chemicals was the photocatalytic reduction of CO2 in the presence of water, known as artificial photosynthesis, Yip said.

"Use of sunlight as an abundant and readily available energy source to drive this important reaction still remains a key challenge for sustainable carbon capture and usage (CCU)," he said.

Titanium dioxide was a well-known semiconductor in the field of photocatalysis, but its band edges lay within the ultraviolet spectra, making it inactive under visible light.

On the other hand, natural leaves were known for their excellent light-harvesting efficiency due to their unique structure with extremely high surface area and photosynthesis function.

In December last year, the UC team made a significant breakthrough by creating artificial TiO2 leaves, which gave unprecedented absorbance and photocatalytic activity improvement under visible light.

The collaboration with City University aimed to fabricate a metal-doped TiO2 catalyst with leaf-like characteristics to yield greater photocatalytic activity under visible light for CCU.

"The proposed research provides a unique opportunity to utilise the properties of both TiO2 and leaves in artificial photosynthesis to convert CO2 into useful products or fuel," said Yip. Endit