Inexpensive Blue Pigment Enables Efficient One-Step Conversion of Carbon Dioxide to Methane

A common blue pigment could help turn carbon dioxide (CO₂) from an industrial waste product into a useful fuel. A joint research team led by Tohoku University's Advanced Institute for Materials Research (WPI-AIMR), in collaboration with Hokkaido University and startup AZUL Energy, has developed a catalyst that converts CO₂ directly into methane (CH₄) with high efficiency using copper phthalocyanine, an inexpensive and readily available blue pigment.

Details were published in the journal Small on August 2, 2026.

The researchers applied the copper phthalocyanine catalyst to a gas diffusion electrode, enabling CO₂ to be reduced to methane in a single electrochemical step. The system achieved a maximum current density of 575 mA cm⁻² and a maximum Faradaic efficiency of 79.5% for methane production, demonstrating that the catalyst can selectively convert CO₂ into methane at high rates.

The catalyst also showed stable performance during long-term operation. At a current density of 150 mA cm⁻², the system maintained methane selectivity above 60% for approximately 80 hours. This durability and selectivity represent an improvement over conventional copper nanoparticle catalysts, which can produce a mixture of different products and make subsequent gas separation more difficult.

Converting CO₂ into useful chemicals and fuels using electricity generated from renewable energy is known as electrochemical CO₂ reduction (ECR). The approach has attracted attention as a potential means of recycling carbon while reducing reliance on fossil resources. Methane is particularly attractive as a target product because it is a widely used gaseous fuel and can potentially be integrated into existing gas infrastructure.

However, producing methane directly from CO₂ is challenging. Electrochemical reduction involves a complex network of reaction pathways, and conventional catalysts can produce several different carbon-containing products alongside methane. Separating and purifying these products adds complexity and energy requirements to the overall process.

To understand why the new catalyst favors methane production, the researchers performed theoretical calculations of the reaction pathways. The calculations showed that the pathway leading to methane formation has a lower energy barrier on the copper phthalocyanine catalyst than pathways leading to other one-carbon products. This suggests that the catalyst can steer the reaction toward methane by favoring a more energetically accessible pathway.

"Converting CO₂ directly into CH₄ in a single, high-efficiency step has been a significant hurdle in carbon recycling," says Professor Hiroshi Yabu of WPI-AIMR, Tohoku University, one of the lead researchers. "By using a low-cost and readily available blue pigment, we have developed an approach that could make this process more practical and scalable. We hope this work will contribute to technologies that convert carbon emissions into useful fuels."

The findings could contribute to the development of next-generation carbon capture and utilization (CCU) technologies. In particular, producing methane directly from CO₂ could reduce the need for downstream separation and purification compared with systems that generate mixtures of gaseous products.

The researchers' next step is to test the catalyst in an electrolyzer using CO₂ captured from actual industrial emissions. They also plan to investigate its use with CO₂ recovered directly from the atmosphere through direct air capture (DAC) technologies. These efforts will help establish the scientific and technological foundations needed to evaluate the catalyst for larger-scale CO₂ utilization.

By combining an inexpensive catalyst with an electrochemical process powered by renewable electricity, the research provides a potential route for converting captured CO₂ into methane in a single step. Further development of the catalyst and electrolyzer system will be needed to determine its performance under practical operating conditions and its potential for integration into carbon recycling technologies.

Publication Details:

Title: Unraveling Structure-Dependent Performance of Cu-N-C Molecular Catalysts for Electrocatalytic CO₂ Methanation

Authors: Tengyi Liu, Xiaofan Hou, Songbo Ye, Kosuke Ishibashi, Yutaro Hirai, Yasutaka Matsuo, Shimpei Ono, Hao Li, and Hiroshi Yabu

Journal: Small

DOI: 10.1002/smll.75041