UC researchers take leaf from nature to catch CO2

UC researchers take leaf from nature to catch CO2

UC researchers have been awarded research funding from the Royal Society of NZ Catalyst Fund to create a synthetic leaf to use or consume the greenhouse gas carbon dioxide.

UC researcher Dr Alex Yip of the University of Canterbury’s Chemical and Process Engineering (CAPE) department, along with UC CAPE PhD student Iman Hashemizadeh and UC Chemistry academic Dr Vladimir Golovko, is working on a collaborative project with Chinese researchers titled: “Decorating Artificial TiO2 leaves for Effective Carbon Dioxide Capture and Usage”.

Global warming caused by greenhouse gases, predominantly carbon dioxide (CO2), is currently the most threatening issue affecting all life forms on Earth, Dr Yip says.

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

This collaboration project between the University of Canterbury and the City University of Hong Kong will learn from nature and use photosynthesis in natural green leaves as the blueprint to develop a “sunlight-driven” process to utilise or consume CO2.

Recently, the New Zealand Project Team has successfully replicated the key structures in natural leaves that are responsible for light-harvesting and photosynthesis using titanium dioxide (TiO2), a proven photocatalyst for CO2 reduction.

Basically, the UC catalysis researchers have been learning from nature. An important approach for converting waste CO2 into useful fuels and chemicals is the photocatalytic reduction of CO2 in the presence of water, known as artificial photosynthesis, Dr Yip says.

“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). Titanium dioxide (TiO2) is a well-known, well-researched semiconductor in the field of photocatalysis; however its band edges lie within the ultraviolet spectra, limiting energy absorption above wavelengths of 400 nm and resulting in it being inactive under visible light.”

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

“In December 2015, our research team at the University of Canterbury made a significant breakthrough and successfully replicated both the micro- and nano-structures of natural leaves for the first time with TiO2 using our self-developed biotemplating method. The new artificial TiO2leaves gave unprecedented absorbance and photocatalytic activity improvement under visible light compared with the analogue, traditional TiO2in particulate form,” Dr Yip says.

With the collaboration of UC and CityU HK in China, this research aims to fabricate a metal-doped titanium dioxide catalyst with leaf-like characteristics to narrow the band gap and yield greater photocatalytic activity under visible light for CCU.

“The key to success is to employ a robust, reliable method to produce metallic nanoparticles, with controllable formulation and size, to decorate the TiO2 leaves via photodeposition. 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. A photo-reactor integrated into a sun tracker will be built and placed on top of a UC building.”

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