Producing synthetic gas from atmospheric carbon dioxide using a transition-metal-free catalyst

Japan has declared carbon neutrality by 2050 as a government target to reduce net greenhouse gas emissions to zero by 2050. In order to substantially reduce CO₂ emissions, it is important not only to control CO₂ emissions through existing processes, but also to develop innovative processes to utilize CO₂ as a resource for production of fuels and chemicals. The core of these efforts is technology to produce syngas, a carbon monoxide and hydrogen gas mixture, from CO₂.

Syngas is produced by using a reverse water gas shift reaction (CO₂+H₂→CO+H₂O) that reduces CO₂ to carbon monoxide by reaction with hydrogen. A highly active transition metal such as platinum, rhodium, nickel, or copper has been considered necessary as a catalyst component to facilitate this reaction.

Prior to the reaction operation, the energy- and cost- intensive processes were necessary to separate and recover CO₂ by a chemical absorption technique and subsequently purify it close to 100 %. An innovative technology, which can directly produce syngas from low-concentration CO₂ without these processes, needs to be developed. Recently, dual-function materials have been attracting attention to enable integrated CO₂ capture and conversion.

In collaboration with Delft University of Technology, researchers in AIST developed a technology for directly producing syngas that is a highly versatile raw material for fuels and chemicals. This technology can utilize CO₂ in exhaust gases from power plants and industrial sectors (~20 %) as well as the low-concentration atmospheric CO₂ (400 ppm; 0.04 %) to produce syngas.

This technology can directly produce syngas, a carbon monoxide and hydrogen gas mixture, by using the dual-function materials to react low-concentration CO₂ with hydrogen derived from renewable energy, without separation and purification processes. While the conventional reaction to reduce CO₂ to carbon monoxide required a catalyst using a transition metal, this technology employs the transition-metal-free dual-function material which has a simple composition with an alkali or alkaline earth metals such as sodium.

In contrast to the conventional method, this technology hardly produces unreacted CO₂. Moreover, a crucial factor in the syngas production namely the H₂/CO ratio is anticipated to be controllable by varying operating conditions such as the hydrogen flow rate.

The work is published in the Journal of CO₂ Utilization.