Outer-sphere Electron Transfer Research Articles

Substrate-Rhodium Cooperativity in Photoinduced ortho-Alkynylation of Arenes.

In the realm of metallaphotocatalytic C-H activation strategy, the direct excitation of the transition metal which plays the dual role of light energy harnessing alongside performing the bond breaking and forming is a rare phenomenon. In this context we have developed the first photo-induced Rh-catalyzed ortho-alkynylation under ambient conditions without the requirement of silver salt, photocatalyst (PC) or any engineered substrate or catalyst. The transformation functions by the specific cooperative effect of a six-membered rhodacycle which is the photo-responsive species. The catalytic system allows the conjugation of arenes with sp3 -rich pharmacophoric fragments. The control experiments as well as the computational studies resolve the mechanistic intricacies for this transformation. An outer sphere electron transfer process from Rh to alkynyl radical is operative for the present photo-induced transformation over the more common oxidative addition or 1,2-migratory insertion pathways.

Substrate‐Rhodium Cooperativity in Photoinduced ortho‐Alkynylation of Arenes

AbstractIn the realm of metallaphotocatalytic C−H activation strategy, the direct excitation of the transition metal which plays the dual role of light energy harnessing alongside performing the bond breaking and forming is a rare phenomenon. In this context we have developed the first photo‐induced Rh‐catalyzed ortho‐alkynylation under ambient conditions without the requirement of silver salt, photocatalyst (PC) or any engineered substrate or catalyst. The transformation functions by the specific cooperative effect of a six‐membered rhodacycle which is the photo‐responsive species. The catalytic system allows the conjugation of arenes with sp3‐rich pharmacophoric fragments. The control experiments as well as the computational studies resolve the mechanistic intricacies for this transformation. An outer sphere electron transfer process from Rh to alkynyl radical is operative for the present photo‐induced transformation over the more common oxidative addition or 1,2‐migratory insertion pathways.

Outer-Sphere Electron-Transfer Process of Molecular Donor–Acceptor Organic Dye in the Dye-Sensitized Photocatalytic System for CO2 Reduction

Outer-Sphere Electron-Transfer Process of Molecular Donor–Acceptor Organic Dye in the Dye-Sensitized Photocatalytic System for CO₂ Reduction

Electro-polymerization rates of diazonium salts are dependent on the crystal orientation of the surface

Electro-polymerization of diazonium salts is widely used for modifying surfaces with thin organic films. Initially this method was primarily applied to carbon, then to metals, and more recently to semiconducting Si. Unlike on other surfaces, electrochemical reduction of diazonium salts on Si, which is one of the most industrially dominant material, is not well understood. Here, we report the electrochemical reduction of diazonium salts on a range of silicon electrodes of different crystal orientations (111, 211, 311, 411, and 100). We show that the kinetics of surface reaction and the reduction potential is Si crystal-facet dependent and is more favorable in the hierarchical order (111) > (211) > (311) > (411) > (100), a finding that offers control over the surface chemistry of diazonium salts on Si. The dependence of the surface reaction kinetics on the crystal orientation was found to be directly related to differences in the potential of zero charge (PZC) of each crystal orientation, which in turn controls the adsorption of the diazonium cations prior to reduction. Another consequence of the effect of PZC on the adsorption of diazonium cations, is that molecules terminated by distal diazonium moieties form a compact film in less time and requires less reduction potentials compared to that formed from diazonium molecules terminated by only one diazo moiety. In addition, at higher concentrations of diazonium cations, the mechanism of electrochemical polymerization on the surface becomes PZC-controlled adsorption-dominated inner-sphere electron transfer while at lower concentrations, diffusion-based outer-sphere electron transfer dominates. These findings help understanding the electro-polymerization reaction of diazonium salts on Si en route towards an integrated molecular and Si electronics technology.

Communication—Determination of the Formation Potential of Solid-Electrolyte Interphase in Amide-Type Ionic Liquids Containing Lithium Salts

The formation potentials of solid-electrolyte interphase (SEI) were investigated in 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)amide (BMPFSA) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing LiFSA and LiTFSA, respectively, by monitoring the redox reaction of ferrocene with high sensitivity. The SEI was found to affect the electrode kinetics of the outersphere electron transfer reaction. The SEIs with the thickness of less than a few nm formed in LiFSA/BMPFSA and LiTFSA/BMPTFSA at 2.4 and 2.5 V vs Li∣Li(I), respectively. The cathodic decomposition of FSA– and TFSA– was considered to be promoted by the interaction with Li+ based on the ab-initio calculation.

Ionic Effect on Electrochemical Behavior of Water-Soluble Radical Polyelectrolytes

Water-soluble redox-active polymers (RAPs) have emerged as attractive electroactive materials for aqueous redox flow batteries because these systems rely on readily available size-exclusion membranes rather than expensive ion-selective membranes. While incorporating ionic units is the most effective strategy for forming water-soluble redox polyelectrolytes, little is known about how charges dictate their electrochemical behavior. Here, we design a series of water-soluble TEMPO (2,2,6,6-tetramethylpiperidyl-1-oxy) radical polyelectrolytes with identical radical distribution but various ionic groups through a sequential postmodification method. Physical and electrochemical characterizations show disparate diffusion coefficients (D) and charge transfer kinetics (k0) of these radical polyelectrolytes at various pH. Particularly, pH exerts a strong impact on k0 of the negatively charged polymer (i.e., with carboxylic acid groups). The bimolecular reaction rate kex determined from redox-induced polymer films shows electrostatic interactions between charged segments can enhance the electron self-exchange reaction rate by ten folds. The results suggest that charge effects are of great importance when designing water-soluble redox polymers for electrochemical applications.

Electronic structure modulation of molybdenum-iron double-atom catalyst for bifunctional oxygen electrochemistry

Exploration of cost effective and high performance electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is becoming the paramount interest towards the emerging renewable energy technologies such as fuel cells, metal air-batteries and water electrolysers, etc. One of such catalysts is single atom catalyst that exhibits well defined active sites with very high atom utilization efficiency but selective mainly towards ORR. We demonstrate one-step synthesis of carbon–nitrogen (CN)-coordinated Fe-Mo double atom catalyst with high atom utilization efficiency towards both ORR and OER. The catalyst exhibits enhanced activity with lower overpotential associated with ORR and OER (ΔE = Ej=10(OER) - E1/2(ORR)) and better mass activity in comparison to that of Mo-N-C and Fe-N-C, even better than the state-of-the-art Pt/C and RuO2 catalysts for ORR and OER, respectively. This place the double atom catalysts in the series of non-precious metal based bifunctional catalysts for overall oxygen electrochemistry and is due to the electronic structure modification around the metal atoms induced by other neighbouring metal atom. The double atom Fe-Mo-N-C exhibits a remarkable and highly durable ORR performance with suppressed peroxide generation due to the muted outer sphere electron transfer mechanism in comparison with the commercially available state-of-the-art Pt/C electrocatalyst. Moreover, Fe-Mo-N-C shows remarkable enhanced overall oxygen electrochemistry at higher temperature (323 K - a temperature 25 K above the room temperature), widening its applicability. Overall, this work paves the way to design multi-atom catalysts towards multi-functional electrocatalytic activities.

Enhanced electrochemical performance of supercritical fluid treated N, P co-doped graphene by dual redox-additives

The low specific energy of carbon-based electrodes in aqueous electrolytes hampers the commercial application of supercapacitors (SCs). Redox-additive addition with conventional electrolyte is an efficient strategy to enhance the specific energy of SC. Here, we demonstrate the constructive synergistic effect and enhance the electrochemical performance by the addition of [Fe(o-phen)3]2+ with [Fe(CN)6]3-/H2SO4. The increase in the specific capacitance (Cs) of N, P co-doped graphene (NPGO) from 290 F g−1 in H2SO4 to 685 F g−1 by the addition of redox-additive [Fe(CN)6]3- with H2SO4. Further enhance in the Cs to 865 F g−1 has been observing by the addition of second redox-additive [Fe(o-phen)3]2+ with [Fe(CN)6]3-/H2SO4. The specific energy of flexible supercapacitor (FSC) uplift 3.6-times using [Fe(o-phen)3]2+(0.63 mM)+[Fe(CN)6](10 mM)/PVA/H2SO4 electrolyte than 6.8 Wh kg−1 of PVA/H2SO4. The enhance in Cs and specific energy has been noticing after the addition of [Fe(o-phen)3]2+ with [Fe(CN)6]3-/H2SO4 due to the outer sphere electron transfer reaction between [Fe(o-phen)3]2+ and [Fe(CN)6]3- with H2SO4.

Acid Catalysis in the Oxidation of Substrates by Mononuclear Manganese(III)-Aqua Complexes.

Acids are known to enhance the reactivities of metal-oxygen intermediates, such as metal-oxo, -hydroperoxo, -peroxo, and -superoxo complexes, in biomimetic oxidation reactions. Although metal-aqua (and metal-hydroxo) complexes have been shown to be potent oxidants in oxidation reactions, acid effects on the reactivities of metal-aqua complexes have never been investigated previously. In this study, a mononuclear manganese(III)-aqua complex, [(dpaq5NO2)MnIII(OH2)]2+ (1; dpaq5NO2 = 2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-ylacetamidate with an NO2 substituent at the 5 position), which is relatively stable in the presence of triflic acid (HOTf), is used in the investigation of acid-catalyzed oxidation reactions by metal-aqua complexes. As a result, we report a remarkable acid catalysis in the six-electron oxidation of anthracene by 1 in the presence of HOTf; anthraquinone is formed as the product. In the HOTf-catalyzed six-electron oxidation of anthracene by 1, the rate constant increases linearly with an increase of the HOTf concentration. Combined with the observed one-electron oxidation product, anthracene (derivative) radical cation, and the substitution effect at the 5 position of the dpaq ligand in 1 on the rate constants of the oxidation of anthracene, it is concluded that the oxidation of anthracene occurs via an acid-promoted electron transfer (APET) from anthracene to 1. The dependence of the rate constants of the APET from electron donors, including anthracene derivatives, to 1 on the driving force of electron transfer is also shown to be well fitted by the Marcus equation of outer-sphere electron transfer. To the best of our knowledge, this is the first example showing acid catalysis in the oxidation of substrates by metal(III)-aqua complexes.

Voltammetric Mapping of Hydrogen Evolution Reaction on Pt Locally via Scanning Electrochemical Cell Microscopy.

The advancement in nanoscale electrochemical tools has offered the opportunity to better understand heterogeneity at electrochemical interfaces. Scanning electrochemical cell microscopy (SECCM) has been increasingly used for revealing local kinetics and the distribution of active sites in electrocatalysis. Constant-contact scanning and hopping scanning are the two commonly used modes. The former is intrinsically faster, whereas the latter enables full voltammetry at individual locations. Herein, we revisit a less used mode that combines the advantages of hopping and constant-contact scan, resulting in a faster voltammetric mapping. In this mode, the nanodroplet cell in SECCM maintains contact with the surface during the scanning and makes intermittent pauses for local voltammetry. The elimination of frequent retraction and approach greatly increases the speed of mapping. In addition, iR correction can be readily applied to the voltammetry, resulting in more accurate measurements of the electrode kinetics. This scanning mode is demonstrated in the oxidation of a ferrocene derivative on HOPG and hydrogen evolution reaction (HER) on polycrystalline Pt, serving as model systems for outer-sphere and inner-sphere electron transfer reactions, respectively. While the kinetics of the inner-sphere reaction is consistent spatially, heterogeneity is observed for the kinetics of HER, which is correlated with the crystal orientation of Pt.

Computational Investigation of the Bisphenolic Drug Metabolism by Cytochrome P450: What Factors Favor Intramolecular Phenol Coupling.

Intramolecular phenol coupling reactions of alkaloids can lead to active metabolites catalyzed by the mammalian cytochrome P450 enzyme (P450); however, the mechanistic knowledge of such an "unusual" process is lacking. This work performs density functional theory computations to reveal the P450-mediated metabolic pathway leading from R-reticuline to the morphine precursor salutaridine by exploring possible intramolecular phenol coupling mechanisms involving diradical coupling, radical addition, and electron transfer. The computed results show that the outer-sphere electron transfer with a high barrier (>20.0 kcal/mol) is unlikely to happen. However, for inter-sphere intramolecular phenol coupling, it reveals that intramolecular phenol coupling of R-reticuline proceeds via the diradical mechanism consecutively by compound I and protonated compound II of P450 rather than the radical addition mechanism. The existence of a much higher radical rebound barrier than that of H-abstraction in the quartet high-spin state can endow the R-reticuline phenoxy radical with a sufficient lifetime to enable intramolecular phenol coupling, while the H-abstraction/radical rebound mode with a negligible rebound barrier leading to phenol hydroxylation can only happen in the doublet low-spin state. Therefore, the ratio [coupling]/[hydroxylation] can be approximately reflected by the relative yield of the high-spin and low-spin H-abstraction by P450, which thus can provide a theoretical ratio of 16:1 for R-reticuline, which is in accordance with previous experimental results. Especially, the high rebound barrier of the phenoxy radical derived from the weak electron-donating ability of the phenoxy radical is revealed as an intrinsic nature. Therefore, the revealed intramolecular phenol coupling mechanism can be potentially extended to several other bisphenolic drugs to infer groups of unexpected metabolites in organisms.

Mechanistic insight into rapid oxygen-atom transfer from a calix-functionalized polyoxovanadate.

We report accelerated rates of oxygen-atom transfer from a polyoxovanadate-alkoxide cluster following functionalization with a 4-tertbutylcalix[4]arene ligand. Incorporation of this electron withdrawing ligand modifies the electronics of the metal oxide core, favoring a mechanism in which the rate of oxygen-atom transfer is limited by outer-sphere electron transfer.

Solvent-mediated outer-sphere CO2 electro-reduction mechanism over the Ag111 surface.

The electrocatalytic CO2 reduction reaction (CO2RR) is one of the key technologies of the clean energy economy. Molecular-level understanding of the CO2RR process is instrumental for the better design of electrodes operable at low overpotentials with high current density. The catalytic mechanism underlying the turnover and selectivity of the CO2RR is modulated by the nature of the electrocatalyst, as well as the electrolyte liquid, and its ionic components that form the electrical double layer (EDL). Herein we demonstrate the critical non-innocent role of the EDL for the activation and conversion of CO2 at a high cathodic bias for electrocatalytic conversion over a silver surface as a representative low-cost model cathode. By using a multiscale modeling approach we demonstrate that under such conditions a dense EDL is formed, which hinders the diffusion of CO2 towards the Ag111 electrocatalyst surface. By combining DFT calculations and ab initio molecular dynamics simulations we identify favorable pathways for CO2 reduction directly over the EDL without the need for adsorption to the catalyst surface. The dense EDL promotes homogeneous phase reduction of CO2via electron transfer from the surface to the electrolyte. Such an outer-sphere mechanism favors the formation of formate as the CO2RR product. The formate can undergo dehydration to CO via a transition state stabilized by solvated alkali cations in the EDL.

Modulation of the kinetics of outer-sphere electron transfer at graphene by a metal substrate.

Solid-supported graphene is a typical configuration of electrochemical devices based on single-layer graphene. Therefore, it is necessary to understand the electrochemical features of such heterostructures. In this work, we theoretically investigated the effect of the metal type on the nonadiabatic electron transfer (ET) at the metal-supported graphene using DFT calculations. We considered five metals Au, Ag, Pt, Cu, and Al on which graphene is physically adsorbed. It is shown that all metals catalyze the ET. The electrocatalytic effect increases in the following series Al < Au ≲ Ag ≈ Cu < Pt. The enhanced ET in the presence of the metal substrate is explained by the hybridization of metal and graphene states, due to which the coupling between the reactant in an electrolyte and metal is increased. Metal-dependent electrocatalytic effect is explained both by different densities of states at the Fermi level of the systems and by differences in the behaviour of the tails of hybridized wave functions in the electrolyte region. The shift of the Fermi level with respect to the Dirac point in graphene when charging at the metal/graphene/electrolyte interface does not affect the kinetics due to the small contribution of graphene states to the electron transfer.

Thermal and photoinduced electron transfer reactions of phthalocyanine complexes of Zn(II) and Cu(II) in acetonitrile.

Phthalocyanine that has four peripheral 2-methoxyphenyl substituents at the α-position and its Zn(II) and Cu(II) complexes were synthesized. Chemical oxidation by the Cu(II) ion and electrochemical oxidation of these metal complexes were investigated spectrophotometrically in acetonitrile. The UV-visible absorption spectra of these metal complexes and their one-electron oxidized π-cation radicals showed no concentration dependence, indicating that these species exist as monomers in solution. Kinetics of the thermal electron transfer reaction from each phthalocyanine complex to Cu2+ and the photoinduced electron transfer reaction of the Zn(II) phthalocyanine complex with V(V) and V(IV) Schiff base complexes were studied using conventional spectrophotometric and transient absorption techniques, and the electron transfer rate constants were analysed using the Marcus cross relationship. The obtained rate constants of the electron self-exchange reaction between the parent phthalocyanine complexes and their π-cation radicals were in the order of 109 to 1011 M-1 s-1 at T = 298.2 K. These large electron self-exchange rate constants are consistent with the phthalocyanine-centred redox reactions where small reorganization energies are required with little structural change during the electron transfer process.

Adiabatic versus non-adiabatic electron transfer at 2D electrode materials

2D electrode materials are often deployed on conductive supports for electrochemistry and there is a great need to understand fundamental electrochemical processes in this electrode configuration. Here, an integrated experimental-theoretical approach is used to resolve the key electronic interactions in outer-sphere electron transfer (OS-ET), a cornerstone elementary electrochemical reaction, at graphene as-grown on a copper electrode. Using scanning electrochemical cell microscopy, and co-located structural microscopy, the classical hexaamineruthenium (III/II) couple shows the ET kinetics trend: monolayer > bilayer > multilayer graphene. This trend is rationalized quantitatively through the development of rate theory, using the Schmickler-Newns-Anderson model Hamiltonian for ET, with the explicit incorporation of electrostatic interactions in the double layer, and parameterized using constant potential density functional theory calculations. The ET mechanism is predominantly adiabatic; the addition of subsequent graphene layers increases the contact potential, producing an increase in the effective barrier to ET at the electrode/electrolyte interface.

Disproportionation of the Uranyl(V) Coordination Complexes in Aqueous Solution through Outer-Sphere Electron Transfer.

Among the linear actinyl(VI/V) cations, the uranyl(V) species are particularly intriguing because they are unstable and exhibit a unique behavior to undergo H+ promoted disproportionation in aqueous solution and form stable uranyl(VI) and U(IV) complexes. This study uses density functional theory (DFT) combined with the conductor-like polarizable continuum model approach to investigate [UO2]2+/+ to [UIVO2] reduction free energies (RFEs) and explores the stability of uranyl(V) complexes in aqueous solution through computing disproportionation free energies (DFEs) for an outer-sphere electron transfer process. In addition to the aqua complex (U1), another three commonly encountered ligands such as chloride (U2), acetate (U3), and carbonate (U4) in aqueous environmental conditions are taken into account. For the U1 complex, the computed 1e- (V/IV) and 2e- (VI/IV) RFEs are in good agreement with experiments. The computed DFEs reveal that the presence of H+ is imperative for the disproportionation to take place. Although the presence of the alkali cations favors the disproportionation to some extent, they cannot fully make the reaction thermodynamically feasible. For the anionic complexes, the high negative charge does not allow for the formation of a cation-cation encounter complex due to Coulombic repulsion. Furthermore, an additional factor is the ligand exchange reaction which is also an energy-demanding step. Therefore, the current study examined the Kern-Orlemann mechanism and our results validate the mechanism based on DFT computed DFEs and propose that for the anionic complexes, an outer-sphere electron transfer is highly probable and our computed protonation free energies further support this claim.

Antioxidative Reactivity of L-Ascorbic Acid and D-Isoascorbic Acid Species towards Reduction of Hexachloroiridate (IV)

The pair [IrCl6]2–/[IrCl6]3– has been demonstrated to be a good redox probe in biological systems while L-ascorbic acid (AA) is one of the most important antioxidants. D-isoascorbic acid (IAA) is an epimer of AA and is widely used as an antioxidant in various foods, beverages, meat, and fisher products. Reductions of [IrCl6]2– by AA and IAA have been analyzed kinetically and mechanistically in this work. The reductions strictly follow overall second-order kinetics and the observed second-order rate constants were collected in the pH region of 0 ≤ pH ≤ 2.33 at 25.0°C. Spectrophotometric titration experiments revealed a well-defined 1 : 2 stoichiometry, namely Δ[AA] : Δ[Ir(IV)] or Δ[IAA] : Δ[Ir(IV)] = 1 : 2, indicating that L-dehydroascorbic acid (DHA) and D-dehydroisoascorbic acid (DHIA) were the oxidation products of AA and IAA, respectively. A reaction mechanism is suggested involving parallel reactions of [IrCl6]2– with three protolysis species of AA/IAA (fully protonated, monoanionic, and dianionic forms) as the rate-determining steps and formation of ascorbic/isoascorbic and ascorbate/isoascorbate radicals; in each of the steps, [IrCl6]2– acquires an electron via an outer-sphere electron transfer mode. Rate constants of the rate-determining steps have been derived or estimated. The fully protonated forms of AA and IAA display virtually identical reactivity whereas ascorbate and isoascorbate monoanions have a significant reactivity difference. The ascorbate and isoascorbate dianions are extremely reactive and their reactions with [IrCl6]2– proceed with the diffusion-controlled rate. The species versus pH and the species reactivity versus pH distribution diagrams were constructed endowing that the ascorbate/isoascorbate monoanionic form dominated the total reactivity at physiological pH. In addition, the value of pKa1 = 3.74 ± 0.05 for IAA at 25.0°C and 1.0 M ionic strength was determined in this work.

KINETICS AND MECHANISM OF THE OXIDATION OF TANNIC ACID BY POTASSIUM TRISOXALATOFERRATE (III) IN AQUEOUS HYDROCHLORIC ACID MEDIUM

The kinetics of the redox reaction between tannic acid (TA) and potassium trisoxalatoferrate (III) trihydrate, (K3[Fe(C2O4)3].3H2O) has been studied in aqueous hydrochloric acid medium. The stoichiometry of the reaction determined by the mole ratio method was observed to be 1:1. The kinetic results showed first order dependence with respect to complex and tannic acid concentrations. The experimental data for the reaction system are consistent with the following rate law:where a = 2.0 × 10-3 mol-1 dm3 s-1 and b = 2.1 × 10-3 mol-2 dm6 s-1 at 420 nm and 27.0 ± 1.0 ºC. The rate of reaction was found to increase with increase in [H+] in the acid range used, but decreased with increase in ionic strength of the reaction medium. While the rate of reaction was observed to decrease with increasing dielectric constant of the reaction medium, the addition of CH3COO-, HCOO-, Ni2+and K+ catalyzed the rate of the reaction. The Michaelis-Menten plot of 1/kobs versus 1/[oxidant] gave a straight line with an insignificant positive intercept. The addition of acrylamide to the partially oxidized reaction mixture did gave a gel in the presence of excess methanol. Based on the experimental data, a plausible mechanism involving outer sphere electron transfer has been proposed for the redox reaction between tannic acid and potassium trisoxalatoferrate (III) trihydrate.

Electrochemical Valorization of Biomass-Derived Feedstocks: Levullinic Acid to 4-Hydroxyvaleric Acid

Fossil fuel-based sources of energy are being gradually replaced by renewable electricity (such as solar, wind, etc), while there is a rising interest in biomass as a sustainable platform to produce fuels and other carbon-based chemicals.1,2 Electrochemistry is thus an attractive approach for the valorization of biomass-derived feedstocks. This approach has shown some advantages compared to traditional thermal- or bio-based chemical conversion such as the amenability to operate directly on aqueous biomass hydrolysate streams, and operability near ambient conditions, which also facilitates distributed scale production.2 This work discusses the electrochemical conversion of levulinic acid (LA) to 4-hydroxyvaleric acid (HVA). HVA is a versatile compound that can be used as a monomer for the production of biodegradable and biocompatible polyesters, in addition to diverse commodities and fine chemicals.3,4 It is projected that the biopolymers industry will reach a global market size of USD 27.9 billion by 2025.5 While prior work has demonstrated that LA can be electrochemically converted into valeric acid (VA) and γ-valerolactone (GVL), among other compounds,2, HVA has only previously been fund as a trace-level intermediate of LA electrochemical reduction into GVL.Here, we show a maximum HVA production rate higher than 40 g L-1 h-1 (i.e., 200 kg L-1 m-2 h-1) at 100% selectivity, and conversion and faradaic efficiency of 81%, while complete LA conversion could also be achieved under lower rates. Our characterization indicates this can further be optimized by reactor design (particularly the mass transport properties) and electrolyte engineering. Though evaluation of different pHs, aqueous supporting electrolytes, temperature, electrode potential, stirring rates, and initial concentration of LA we also elaborate on mechanistic underpinnings of the reaction selectivity, proposing that the formation of VA and GVL is through surface-mediated reactions, while HVA is formed via an outer sphere electron transfer (OSET) route (Fig.1). References (1) npj Clim. Atmos. Sci. 2019, 2 (1), 35.(2) ACS Energy Lett. 2021, 1205–1270. https://doi.org/10.1021/acsenergylett.0c02692.(3) . J. Biotechnol. 2015, 210, 38–43.(4) J. Agric. Food Chem. 2019, 67 (9), 2540–2546.(5) Global Bioplastics & Biopolymers Market Outlook 2020-2025 https://www.globenewswire.com/news-release/2020/04/17/2017839/0/en/Global-Bioplastics-Biopolymers-Market-Outlook-2020-2025.html (accessed April 22, 2021). Figure 1