The promise of Janus nanostructures for solar photocatalysis

Solar photocatalysis is something of a great, green promise. The more than 40-year-old technology has the legitimate potential to address some of today’s most pressing global needs, like producing clean-burning hydrogen fuel, capturing and sequestering carbon dioxide from the atmosphere, remediating toxic waste, and sterilizing drinking water.

But while these applications have been demonstrated in the laboratory, practical solar photocatalysis cannot be implemented on a massive scale unless we find better catalysts. Most of the catalytic materials developed to date are not suitable for large-scale application because they suffer from poor visible light response, chemical stability issues and high cost of fabrication.

What the field needs are materials that are highly stable, more efficient and cheaper to produce. One promising area of research today focuses on improving the performance and stability of semiconductor catalysts through nanostructuring, doping or adding low-cost “co-catalyst” materials.

In a new review, Chauhan et al. explore recent efforts to develop co-catalysts based on anisotropic, bi-phasic heterodimer materials — otherwise known as “Janus catalysts,” which are named after the two-faced Greek god who guarded dungeon doors and palace gates.

Janus catalysts are two-faced because of their anisotropy, which separates sites for reduction and oxidation reactions. Such a separation prevents reaction intermediates from mixing with each other, thereby preventing back-reactions and improving catalytic efficiency. Improved charge separation, light absorption and amplification of electric near fields also serve to increase the overall efficiency of the catalyst, though further research will be needed to unlock their full potential, Chauhan said.

“Hopefully, with continued and dedicated research in this field, it will be possible to realize cheap and efficient catalysts, which will enable the development of some early large-scale applications for photocatalysis,” he added.

Source: “Janus nanostructures for heterogeneous photocatalysis,” by Aditya Chauhan, Monisha Rastogi, Paul Scheier, Chris Bowen, Ramachandran Vasant Kumar, and Rahul Vaish, Applied Physics Reviews (2018). The article can be accessed at https://doi.org/10.1063/1.5039926 .