Hybrid bio-inorganic system for water splitting

(Nanowerk News) With the consumption of massive fossil fuel, significant amounts of CO2 has been released into the atmosphere, and caused serious environmental problems.
A hybrid bio-inorganic system can effectively combine the advantage of electrocatalysis and biosynthesis, and achieve the efficient conversion of CO2 to high value-added compounds.
However, intimate coupling of electrocatalysis and biosynthesis requires electrocatalysts that possess both high catalytic performance and excellent biocompatibility, which is a bottleneck of developing such catalysts.

Nickel nanoparticles-embedded N-doped carbon nanotubes

In the ChemSusChem journal ("Water Splitting–Biosynthetic Hybrid System for CO2 Conversion using Nickel Nanoparticles Embedded in N-Doped Carbon Nanotubes"), a joint research team from the College of Chemical and Biological Engineering at Zhejiang University has developed a novel Ni nanoparticles-embedded N-doped carbon nanotubes (Ni@N-C) complex for hydrogen evolution reaction.
In the Ni@N-C hybrid, the Ni nanoparticles were successfully encapsulated in N-doped carbon nanotubes. Benefiting from the unique structure, the Ni@N-C hybrid achieved high HER catalytic activity and excellent biocompatibility simultaneously in the hybrid bio-inorganic system.

Efficient conversion of CO2 to poly-β-hydroxybutyrate (PHB) in a water splitting–biosynthetic hybrid system

The Ni@N-C hybrid was further coupled with a hydrogen-oxidizing autotroph, Cupriavidus necator H16, to build a water splitting-biosynthetic hybrid system for CO2 conversion to PHB.
In the hybrid system, the Ni nanoparticles embedded structure effectively isolated the Ni from the bacteria and avoided the direct contact between Ni and bacteria.
Also, encapsulating Ni nanoparticles into the N-C nanotubes prevented Ni2+ ions leaching, which significantly improved the biocompatibility of Ni@N-C hybrid.
In addition, the embedding of Ni nanoparticles and doping of N atoms into the carbon nanotubes could guarantee the high HER activity and good stability of the Ni@N-C hybrid in the system. Finally, a maximal PHB production of 384.30 ± 6.53 mg L-1 with the maximum PHB production rate of 207.86 ± 4.03 g m-2 L-1 d-1 were obtained, which is comparable to that of Pt/C catalyst.
The low cost of Ni@N-C hybrid makes it a good alternative to commercial Pt/C in building these hybrid systems. This work provides an important strategy for designing electrocatalysts with both high HER activity and excellent biocompatibility in bio-inorganic hybrid systems for efficient conversion of CO2 to high value products.
Source: Zhejiang University
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