A review of global current techniques and evaluation methods of photocatalytic CO2 reduction

Nowadays, energy issues that derive from mass energy consumption and the climate change by the increasing concentration of carbon dioxide (CO2) in the atmosphere is a critical problem that people around the world are facing. To tackle these problems, the uses of renewable energy that mainly generates electricity from renewable energy sources have been increasing. Photocatalysts have the potential to solve the problems as photocatalysts reduce CO2 to methane, methanol and other products that can be used as fuels by using solar energy that is an abundant energy source in the world. For photocatalytic CO2 reduction, a variety of material structures and combinations are studied in addition to conventional material structures that are support, doping, and Z-scheme. Though several evaluation units that originate from diverse structures of composites and reactors have been studied, it is found that the evaluation methods need to be standardized. It is suggested that the light source for photocatalytic CO2 reduction should be artificial solar light. The unit used for the evaluation is proposed to be the conversion efficiency to demonstrate the ratio of the total energy of products (EP) to irradiation energy received at the reactor.