Glucose Conversion on Ni-based Electro-Catalysts – GluCoNiC

- Ni-based nanomaterials will be prepared by electrochemical and soft chemistry methods.
- Analytical tools (High Performance Liquid Chromatography, and Nuclear Magnetic Resonance) will be used to determine selectivity of electrochemical reactions.
- Operando Fourier Transform Infra-Red Spectroscopy and online Differential Electrochemical Mass Spectrometry will be used to investigate reaction mechanisms.
- Stability of the catalysts towards degradation will be investigated by identical-location transmission electron microscopy (IL-TEM) and on-line inductively coupled plasma mass spectrometry (ICP-MS).
- A continuous flow electrochemical reactor will be developed to produce gluconic acid and sorbitol.

To establish appropriate benchmarks, glucose, gluconic acid and sorbitol oxidation were first studied on Pt, Pd and Au gold in 0.1 M NaOH. By combining cyclic voltammetry (CV), differential electrochemical mass spectrometry (DEMS), and in situ Fourier transform infrared (FTIR) spectroscopy, the reaction mechanism was unveiled. The nature of the reactant has a strong impact on the onset of the oxidation reaction. The anomeric function of glucose is oxidized at low potentials on the three surfaces, while gluconic acid and sorbitol poison the surface at low potentials. In addition, the nature of the metal surface leads to different reaction pathways. It is proposed that the oxidation of glucose initiates via the partial dissociative adsorption of glucose into glucose adsorbates and adsorbed H (Had) for the three metal surfaces. These adsorbates are partially combined into H2 on Au and oxidized into water on Pt and Pd.
The glucose oxidation (GOR) was then studied on Ni and on bimetallic NiAu electrodes. To this end, the procedures for Ni electrodeposition on glassy carbon (GC), on Vulcan XC-72 carbon, and on polycrystalline Ni have been optimized, conditions for maximizing the total and/or the specific surface area of Ni have been determined. Deposition in the interval of intermediate overpotentials allows to generate Ni nanoparticles, while deposition at high overpotentials (under the conditions of vigorous hydrogen evolution) results in formation of highly porous Ni foams. The GOR starts on Ni at high anodic potentials, and requires the presence of both the Ni(OH)2 and NiOOH sites. This conclusion is supported by kinetic modeling.
Combining Ni with Au allows to further improve the rate of the GOR, while simultaneously significantly decreasing the Au content. Bimetallic NiAu electrodes were prepared by electrodeposition on various substrates. Their surface composition can be conveniently controlled by monitoring the open circuit potential after the deposition as confirmed by the X-ray photoelectron spectroscopy analysis. According to high resolution transmission electron microscopy coupled with EDX, nanoparticles adopt core-shell structure. NiAu nanoparticles covered by Au show the most promising results for the glucose oxidation.
The first version of the batch electrosynthesis reactor was implemented. Furthermore, a continuous filter press-type reactor equipped with foam-type electrodes, and a separator, with a flow configuration parallel to the latter, was implemented. Studies in a continuous membrane reactor were performed and products were analyzed with HPLC.

The project contributes to the implementation of the French national strategy for bioeconomy validated in 2017. Our ambition is to enable France to move from a fossil fuel-based to a renewable carbon economy. It contributes to the development of cost- and energy-effective means for the transformation and refinery of glucose issued from lignocellulosic biomass (non-edible agricultural, forestry or marine) into high value-added chemicals. Compared to the existing technologies, such an electrochemical process will have a low environmental impact, will help in laying foundation of the French leadership in the next generation of electrochemical clean organic synthesis technologies, and contribute to the fight against climate change.

Théo Faverge, Bruno Gilles, Antoine Bonnefont, Frédéric Maillard, Christophe Coutanceau, and Marian Chatenet, In Situ Investigation of d-Glucose Oxidation into Value-Added Products on Au, Pt, and Pd under Alkaline Conditions: A Comparative Study, ACS Catal. 2023, 13, 4, 2657–2669
doi.org/10.1021/acscatal.2c05871

Neha Neha, Thibault Rafaïdeen, Théo Faverge, Frédéric Maillard, Marian Chatenet, and Christophe Coutanceau, Revisited Mechanisms for Glucose Electrooxidation at Platinum and Gold Nanoparticles, Electrocatalysis, 2023, 14 (1), pp.121-130; doi.org/10.1007/s12678-022-00774-y

Lignocellulosic biomass-derived sugars (like glucose) provide a renewable and almost inexhaustible carbon feedstock for sustainable production of fine chemicals. Gluconic acid and sorbitol belong to the top-30 list of value-added chemicals from biomass. Currently, glucose conversion into sorbitol and gluconic acid is performed using either bio-technological or heterogeneous catalytic routes. Electrochemical conversion, with its low environmental footprint, high energy efficiency, tunability and controllability of the process conversion and selectivity, is perfectly compatible with the biomass transformation considering its composition (carbohydrates) and high water content, and becomes increasingly attractive with the growth of the renewable electricity production. The objective of this project is to develop a continuous electrocatalytic reactor, free from strategic platinum group metals, and allowing simultaneous production of gluconic acid at the anode and sorbitol at the cathode. To this end, we will synthesize mono- and bimetallic Ni-based nanomaterials, and systematically study them under well-defined conditions in an electrochemical cell in alkaline media. Fine control of the Ni surface state and addition of other metals will serve as tools to tune the electrocatalytic activity of Ni in the glucose oxidation and reduction reaction. Electrochemical methods, in situ spectroscopic and analytical tools combined with kinetic modeling will aid us determine rate and selectivity of electrochemical reactions depending on the electrode potential, glucose concentration, pH and temperature, and propose reaction mechanisms. Stability of the catalysts towards degradation will be investigated by identical-location transmission electron microscopy and on-line inductively coupled plasma mass spectrometry to probe textural degradation, metal dissolution and nanoparticle detachment. These studies will help designing active and stable Ni-based catalysts and defining operational modes ensuring high durability, selectivity and energy-efficiency. Finally, a continuous flow electrochemical reactor comprising industrially-relevant Ni foam/felt-based electrodes will be developed, allowing simultaneous, selective and energy-efficient production of gluconic acid at the anode and sorbitol at the cathode. The project contributes to the implementation of the French national strategy for bioeconomy validated in 2017. Our ambition is to enable France to move from a fossil fuel-based to a renewable carbon economy. It contributes to the development of cost- and energy-effective means for the transformation and refinery of glucose issued from lignocellulosic biomass (non-edible agricultural, forestry or marine) into high value-added chemicals. Compared to the existing technologies, such an electrochemical process will have a low environmental impact, will help in laying foundation of the French leadership in the next generation of electrochemical clean organic synthesis technologies, and contribute to the fight against climate change.