Creating a Low‐Potential Redox Polymer for Efficient Electroenzymatic CO₂ Reduction

Abstract

Increasing greenhouse gas emissions have resulted in greater motivation to find novel carbon dioxide (CO 2 ) reduction technologies,where the reduction of CO 2 to valuable chemical commodities is desirable.M olybdenum-dependent formate dehydrogenase (Mo-FDH) from Escherichia coli is ametalloenzyme that is able to interconvert formate and CO 2 . We describe al ow-potential redox polymer,s ynthesized by af acile method, that contains cobaltocene (grafted to poly-(allylamine), Cc-PAA) to simultaneously mediate electrons to Mo-FDH and immobilize Mo-FDH at the surface of acarbon electrode.T he resulting bioelectrode reduces CO 2 to formate with ah igh Faradaic efficiency of 99 AE 5% at am ild applied potential of À0.66 Vvs. SHE.Owing to the soaring demand for energy,f ossil fuel combustion has resulted in vast amounts of greenhouse gases,e specially carbon dioxide (CO 2 ), being released into the atmosphere. [1] CO 2 causes global warming and climate change,leading to an increase in the sea level and biodiversity loss. [1c, 2] CO 2 can be converted into acheap and abundant C 1 feedstock, [3] in addition to being used for the storage of renewable energy; [4] however, the process of CO 2 fixation is challenging owing to the kinetic and thermodynamic stability of CO 2 . [5] Thus an effective catalyst that can capture CO 2 and reduce it to carbon fuels or chemical commodities is desirable. Them ost common catalysts are organometallic complexes, but selectivity is often limited and large overpotentials are required. [6] Biocatalysts such as enzymes are an attractive alternative to organometallic complexes owing to their high selectivity and catalytic efficiency under mild conditions (such as aqueous solutions of near-neutral pH, room temperature, and ambient pressure). [7] Formate dehydrogenases (FDHs) have been largely explored in enzymatic biotechnologies where formate oxidation to CO 2 can result in the production of electrical energy. [8] However,s ome FDHs (typically those containing metal cofactors) can function as CO 2 reductases, and are capable of interconverting CO 2 and formate [Equation (1)]. [9] FDHs can be classified into two categories:t he nicotinamide adenine dinucleotide (NAD + )-dependent FDH and metal-dependent FDHs.T he NAD + -dependent FDH, which requires the unstable,e xpensive,a nd diffusive cofactor (NAD + or NADH) as the electron donor or acceptor, is well understood but typically has poor CO 2 reduction activity. [10] Furthermore,the electroreduction of NAD + commonly results in the formation of enzymatically inactive dimers. [11] Themore recently studied metal-dependent FDHs, which typically contain molybdenum (Mo-FDH) or tungsten (W-FDH), are more efficient biocatalysts for CO 2 reduction. [9b, 12] In addition, their tightly associated cofactors make them attractive biocatalysts for immobilized electroenzymatic biotechnologies.W -FDH has been reported by Reda and coworkers for its high efficiency in reversibly interconverting CO 2 and formate. [5] TheMo-FDH from E. coli of the formate hyd...

Preventing the coffee-ring effect and aggregate sedimentation by in situ gelation of monodisperse materials

“…These requirements are fundamental for numerous applications based on active films such as organic semiconductors 15 for photovoltaics, 16 inorganic catalysts for water splitting, 17 or (bio-)molecular catalysts for sensing 18 and energy conversion. 19 , 20 The thickness of the film is of particular importance since it defines the factors governing the catalytic current or photocurrent generation. 21 – 24 Therefore, if the thickness is heterogeneous because of the presence of aggregates, some parts of the film will have sub-optimal dimensions which will be detrimental to the overall catalytic or photoactive performances.…”

Strategies for Bioelectrochemical CO2 Reduction

“…It is proposed that either the EcFDH‐H is inactivated upon purification, or the reduced methyl viologen does not have the driving force to overcome the energy barrier to directly transfer the electron to the Mo active site center; instead, it reduces the [4Fe‐4S] cluster which subsequently reduces the Mo site in an unfavored manner . Inspired by this work, Minteer and colleagues developed a low potential redox polymer, cobaltocene poly(allylamine) (Cc‐PAA) with E=−0.576 V vs. SHE, for efficient CO 2 reduction with a high faradaic efficiency of 99 % (Figure C) . Such a redox polymer has the potential to facilitate electron transfer for other types of metal‐dependent electroactive FDHs as well.…”

“…[14] Inspired by this work, Minteera nd colleagues developed al ow potentialr edox polymer,c obaltocenep oly(allylamine) (Cc-PAA) with E = À0.576 Vv s. SHE, for efficient CO 2 reduction with a high faradaic efficiency of 99 %( Figure 1C). [26] Such ar edox polymerh as the potentialt of acilitatee lectron transfer for other types of metal-dependente lectroactive FDHs as well. This example demonstrates the potential of couplinge nzymes to redox polymers to achieve enhanced stability anda ctivity at the electrode;b yu sing this strategy with ah ighly active FDH, as uperior carbon dioxide reduction system could be devised.…”

Surface Modification of Tin Dioxide via (Bi, S) Co‐Doping for Photoelectrocatalytic Reduction of CO2 to Formate

“… is the molar amount of formate produced; Z is the number of transferred electron to form formate ( Z is 2 here); F is the Faraday constant, 96485 C mol −1 ; Q is the total electrons passed the electrode within one hour reaction …”

“…successfully reduced CO 2 into formate with faradaic efficiency of 89 % via electrochemical methods when mesoporous SnO 2 nanosheets load onto carbon cloth as a cathode, however the overpotential is as high as 0.88 V. Therefore, the large overpotential for activating CO 2 to CO 2 .− intermediate limits further development. Meanwhile, the slow electron transfer and the inevitably competing hydrogen evolution reaction (HER) are the major obstacle as well. Nowadays, photochemical CO 2 reduction is also considered as a promising and environment friendly technique, whereas the lower CO 2 conversion efficiency restricts its application.…”