Hierarchical TiN‐Supported TsFDH Nanobiocatalyst for CO₂ Reduction to Formate

Abstract

The electrochemical reduction of CO2 to value‐added products like formate represents a promising technology for the valorization of carbon dioxide. We propose a proof‐of‐concept bioelectrochemical system (BES) for the reduction of CO2 to formate. For the first time, our device employs a nanostructured titanium nitride (TiN) support for the immobilization of a formate dehydrogenase (FDH) enzyme. The hierarchical TiN nanostructured support exhibits high surface area and wide pore size distribution, achieving high catalytic loading, and is characterized by higher conductivity than other oxide‐based supports employed for FDHs immobilization. We select the oxygen‐tolerant FDH from Thiobacillus sp. KNK65MA (TsFDH) as enzymatic catalyst, which selectively reduces CO2 to formate. We identify an optimal TiN morphology for the enzyme immobilisation through enzymatic assay, reaching a catalyst loading of 59 μg cm−2 of specifically‐adsorbed TsFDH and achieving a complete saturation of the anchoring sites available on the surface. We evaluate the electrochemical CO2 reduction performance of the TiN/TsFDH system, achieving a remarkable HCOO− Faradaic efficiency up to 76 %, a maximum formate yield of 44.1 μmol mg−1FDH h−1 and high stability. Our results show the technological feasibility of BES devices employing novel, nanostructured TiN‐based supports, representing an important step in the optimization of these devices.

Renewable Hydrogen Production and Storage Via Enzymatic Interconversion of CO2 and Formate with Electrochemical Cofactor Regeneration

“…The advantages highlighted for this material as a support are its high surface area, pore size distribution and conductivity. The system exhibited a faradaic efficiency of 76 % and a maximum product yield of 44 μM mg FDH −1 h −1 at −0.15 V and −0.75 V (vs RHE) respectively, figures that are particularly encouraging, compared to other BES reported [136] …”

“…The system exhibited a faradaic efficiency of 76 % and a maximum product yield of 44 μM mg FDH À 1 h À 1 at À 0.15 V and À 0.75 V (vs RHE) respectively, figures that are particularly encouraging, compared to other BES reported. [136] Nafion is often used as binder to immobilize FDH onto the electrode to create a biocathode. Hernández-Ibáñez et al [117] propose an effective electrochemical FA-producing system where Nafion was used to co-immobilize CbFDH and a rhodium complex mediator on a nanoporous carbon electrode.…”

Polyethylenimine‐Grafted Silica Nanoparticles Facilitate Enzymatic Carbon Dioxide Conversion

“…The conversion of carbon dioxide (CO 2 ) to industrial products has attracted significant research interest in recent years, and green biocatalysis is considered an effective means to implement this conversion [1]. Many oxidative enzymes (e.g., carbon monoxide dehydrogenase [2], nitrogenase [3], formate dehydrogenase [4]) and non-oxidative enzymes (e.g., phosphoenolpyruvate carboxylase, PEPCase [5]) have been utilized for CO 2 conversion. Notably, these enzymatic CO 2 conversions need to react in aqueous solution, and the main carbon source of many CO 2 -converting enzymes (e.g., PEPCase) is bicarbonate (HCO 3 -) [6].…”