Sustainable approach for CO2 hydrogenation to formic acid with Ru single atom catalysts on nitrogen-doped carbon prepared from green algae

초록

Ruthenium catalysts supported on nitrogen-doped carbon (NDC) have gained attention due to their exceptional catalytic performance for CO2 hydrogenation to formic acid a key solution to mitigate CO2 emissions. However conventional methods for preparing NDC typically rely on petrochemical compounds which are not environmentally friendly. Herein we propose a sustainable and innovative approach by employing protein-rich green algae as a source to prepare NDC for Ru catalysts. To maximize the CO2 reduction effect flue gas exhausted from industrial processes was utilized as a CO2 feed to cultivate the green algae in a photobioreactor. The harvested green algae were pyrolyzed at 800 °C under an N2 atmosphere to prepare the NDC. After the metalation of Ru on prepared NDC the Ru catalysts exhibited a turnover number of 7599 for CO2 hydrogenation which demonstrated the potential of green algae as a raw material for NDC. However the catalysts were deactivated due to the leaching or agglomeration of weakly bound Ru analyzed by experimental and theoretical investigations. We applied a NaBH4 treatment to stabilize the Ru active sites and the treated catalysts retained 99.6 % of their initial catalytic activity after five recycling tests. Furthermore Ru on NDC achieved a cumulative turnover number of 16000 after 24 h. This study offers a sustainable and eco-friendly method for reducing CO2 emissions combining the cultivation of green algae with waste flue gas and the production of formic acid via CO2 hydrogenation using improved Ru catalysts on algae-derived NDC. © 2024 The Author(s)

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