[FeFe]-Hydrogenase Encapsulated in Zeolitic Imidazolate Framework (ZIF)‑8 Nanoparticles as a Robust Biocatalyst for Photocatalytic Hydrogen Production

[FeFe]-hydrogenase (HydA) is an active biocatalytic enzyme for solar-to-hydrogen (H2) conversion. However, stability is a main challenge that limits practical applications. This work aims to encourage the efficiency of HydA by encapsulating it in the zeolitic imidazolate framework-8 (ZIF-8) as a synthetic protective shield. The construction of HydA@ZIF-8 nanoparticles, with an average diameter of 700–1000 nm, at ambient conditions can preserve HydA activity within a spatially confined microenvironment, as characterized by scanning electron microscopy and X-ray diffraction analysis. Based on MV•+-dependent H2 production activity and kinetic analysis, both the stability and efficiency of HydA@ZIF-8 surpass those of free HydA and whole-cell biocatalysts over a wider range of pH and temperature. The achievement of robust HydA@ZIF-8 construction represents a significant step forward in the development of biocatalysts for various future applications

The Role of Adsorbed CN and Cl on an Au Electrode for Electrochemical CO₂ Reduction

Electrochemical CO₂ reduction is one of the promising ways to convert CO₂ to value-added products such as CO. Many studies have dealt with suppressing the hydrogen evolution reaction (HER) and increasing the CO₂ reduction reaction (CO₂RR) through modification of the metal surface with additives such as anchoring agent, anion, etc. However, there are only a few studies about modifying the Au surface with additives. We present here a theoretical prediction that the addition of the CN and Cl species on an Au electrode would enhance the electrochemical CO₂RR due to van der Waals interactions with these large anionic species. On the basis of this suggestion, we then prepared functionalized Au electrodes by electroplating in an aqueous solution containing CN^– or Cl^– and experimentally verified that the CO₂RR of functionalized Au indeed shows exceptional CO₂RR activity in comparison to pristine Au

Silver Nanowire/Carbon Sheet Composites for Electrochemical Syngas Generation with Tunable H₂/CO Ratios

Generating syngas (H₂ and CO mixture) from electrochemically reduced CO₂ in an aqueous solution is one of the sustainable strategies utilizing atmospheric CO₂ in value-added products. However, a conventional single-component metal catalyst, such as Ag, Au, or Zn, exhibits potential-dependent CO₂ reduction selectivity, which could result in temporal variation of syngas composition and limit its use in large-scale electrochemical syngas production. Herein, we demonstrate the use of Ag nanowire (NW)/porous carbon sheet composite catalysts in the generation of syngas with tunable H₂/CO ratios having a large potential window to resist power fluctuation. These Ag NW/carbon sheet composite catalysts have a potential window increased by 10 times for generating syngas with the proper H₂/CO ratio (1.7–2.15) for the Fischer–Tropsch process and an increased syngas production rate of about 19 times compared to that of a Ag foil. Additionally, we tuned the H₂/CO ratio from ∼2 to ∼10 by adjusting only the quantity of the Ag NWs under the given electrode potential. We believe that our Ag NW/carbon sheet composite provides new possibilities for designing electrode structures with a large potential window and controlled CO₂ reduction products in aqueous solutions