Promising triazole molecular catalyst enables efficient electroreduction of carbon dioxide to methane

The efficient conversion of carbon dioxide (CO₂)—one of the main compounds contributing to climate change—into useful fuels and chemicals is a long sought-after research goal. Recent studies have introduced various catalysts that could be used to initiate the so-called electrochemical CO₂ reduction reaction in electrolyzers (i.e., devices that drive specific chemical reactions using electricity).

The CO₂ reduction reaction is the chemical process via which CO₂ molecules are reduced, ultimately forming other chemicals or fuels. Most of the catalysts previously employed to initiate this reaction in electrolyzers are metallic, such as copper, silver and gold.

Metal-based catalysts, however, often exhibit a limited tunability, which means that leveraging them to precisely reduce CO₂ into specific chemical products can be challenging. Some studies have thus been assessing the potential of alternative non-metallic catalysts for converting CO₂ into desirable fuels and chemicals.

Researchers at the Chinese University of Hong Kong, University of Auckland and National Yang Ming Chiao Tung University recently introduced a new promising triazole molecular catalyst for the efficient electrochemical reduction of CO₂ into methane (CH₄). A preliminary system utilizing this catalyst, presented in a paper published in Nature Energy, was found to reliably convert CO₂ into CH₄, exhibiting both good efficiency and turnover frequency.

“Organic molecular catalysts, which are more acutely tunable than metal catalysts, are still unable to catalyze CO₂ to hydrocarbons under industrially relevant current densities for long-term operation, and the catalytic mechanism is still elusive,” Zhanyou Xu, Ruihu Lu and their colleagues wrote in their paper. “We report 3,5-diamino-1,2,4-triazole-based membrane electrode assemblies for CO₂-to-CH₄ conversion with Faradaic efficiency of (52 ± 4)% and turnover frequency of 23,060 h⁻¹ at 250 mA cm⁻².”

The researchers devised an initial system for reducing CO₂ using their triazole molecule-based catalyst and explored its performance in a series of tests, where they ran it at a current of 10A for 10 hours of electrolysis. Their findings were highly promising and offered them valuable insight into the process through which their system converted CO₂ into CH₄.

“Our mechanistic studies suggest that the CO₂ reduction at the 3,5-diamino-1,2,4-triazole electrode proceeds through the intermediary *CO₂–*COOH–*C(OH)₂–*COH to produce CH₄ due to the spatially distributed active sites and the suitable energy level of the molecular orbitals,” wrote Xu, Lu and their colleagues. “A pilot system operated under a total current of 10 A (current density = 123 mA cm⁻²) for 10 h is able to produce CH₄ at a rate of 23.0 mmol h⁻¹.”

Overall, the findings of this recent study highlight the potential of triazole molecular catalysts for enabling the scalable and selective electroreduction of CO₂. The promising catalyst they identified, namely 3,5-diamino-1,2,4-triazole (DAT), could soon be studied and evaluated further by other research teams, or could inspire the design of similar catalysts for converting CO₂ into other useful chemicals.

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