Carbon dioxide is one of the main greenhouse gases that cause global warming. A joint research team led by City University of Hong Kong (CityU) has developed a new photocatalyst that selectively and efficiently produces methane fuel from carbon dioxide using sunlight.
Inspired by photosynthesis in nature, carbon dioxide is efficiently converted to methane fuel using a newly developed solar catalyst. By the way, it is made of copper-based materials, which makes it more affordable.
In general, converting carbon dioxide (CO₂) into methane (CH₄) fuels using a photocatalyst is a thermodynamically challenging task. The fact is that the process of chemical reduction involves the simultaneous transfer of eight electrons.
Copper oxide (Cu₂O), a semiconductor material, has been used as both a photocatalyst and an electrocatalyst to reduce carbon dioxide to other chemical products such as carbon monoxide and methane. However, poor stability and non-selective reduction, which causes the formation of many different products, have limited its use. Separating and purifying these products from the mixture can be very challenging. This creates a technological barrier to large scale applications. In addition, copper oxide can corrode easily after short exposure.
To overcome these problems, the scientists synthesized a new photocatalyst by encapsulating copper oxide in copper-based metal-organic frameworks (MOFs). In this way, they were able to control the transfer of electrons and selectively produce pure methane gas. Compared to bare MOF copper oxide, coated copper oxide stably reduces carbon dioxide to methane when exposed to visible light in nearly double the yield. In addition, MOF clad copper oxide was stronger, and the maximum absorption of carbon dioxide was almost seven times that of uncoated copper oxide.
The study was conducted by Dr. Ng Yun-hau, Associate Professor at the School of Energy and Environment (SEE), in collaboration with researchers from Australia, Malaysia and the UK. The results are published in the scientific journal Angewandte Chemie.