Efficient CO2 conversion by biocompatible N-doped carbon nanosheets coupled with Ralstonia eutropha: synergistic interactions between microbial and inorganic catalysts

Abstract

Electricity-to-chemical production from a hybrid microbial–inorganic catalytic system relies upon biocompatible and efficient catalysts for hydrogen evolution reactions (HERs). Herein, metal-free nitrogen-doped carbon nanosheets (NC) with no metal leaching and little generation of reactive oxygen species were synthesized to develop an efficient hybrid catalytic system for converting CO₂ to poly-β-hydroxybutyrate. A yield of 538 mg L⁻¹ with an electricity-to-organic efficiency of 10.5% was obtained, which outcompetes most of the previous achievements. The coupling of NC with Ralstonia eutropha H16 reduced the HER overpotential by 200 mV. It was attributed to the doped N atoms facilitating the immobilization of bacteria on the catalysts to enhance hydrophilicity. Besides, the [NiFe]-hydrogenase from R. eutropha accelerates the desorption of H₂ and may provide an effective HER catalytic center on the catalysts. This study reveals the synergistic interactions between metal-free catalysts and R. eutropha H16 to promote H₂ production and CO₂ conversion.