Selective Electro-Oxidation of Glycerol to Dihydroxyacetone by PtAg Skeletons

Efficient electrocatalysis conversion of glycerol to formate in alkaline solution by nickel (oxy)hydroxide supported cobalt nanoneedle arrays

Electrochemical oxidation of glycerol into value-added chemicals represents a sustainable approach for not only valorizing biomass resources but also improving the energy efficiency of electrolysis by replacing the kinetically sluggish oxidation of water at the anode. Here, we present a nickel (oxy)hydroxide supported cobalt nanoneedle arrays catalyst (CoNA-NiOH/NF-2) for effective oxidation of glycerol. The loaded Co(OH)2 forms more oxygen defects, increases the active sites, and enhances the performance of glycerol oxidation. The CoNA-NiOH/NF-2 catalyst significantly reduces energy consumption by achieving a current density of 10 mA cm-2 at a low voltage of 1.22 V vs. RHE, and 100 mA cm-2 at 1.42 V vs. RHE, which is approximately 240 mV lower than oxygen evolution reaction (OER). Additionally, the Faraday efficiency of formate generation reached 98 %. The growth of renewable energy sources will greatly benefit from this strategy, which calls for replacing anodic OER with biomass oxidation.

Electrochemical Cycling of Liquid Organic Hydrogen Carriers as a Sustainable Approach for Hydrogen Storage and Transportation

Hydrogen (H2), as a high-energy-density molecule, offers a clean solution to carry energy. However, the high diffusivity and low volumetric density of H2 pose a challenge for long-term storage and transportation. Liquid organic hydrogen carriers (LOHCs) have been suggested as a strategic way to store and transport hydrogen in stable molecules. More so, electrochemical LOHC cycling renders an opportunity to utilize renewable energy for hydrogen storage and transportation toward the goal of eliminating carbon emissions. In this Perspective, examples of electrochemical reactions of organic molecules and their suitability for LOHC couples are examined. A comparative carbon footprint assessment of electrochemical LOHC cycling processes against thermochemical and hybrid LOHC cycling processes was performed. The electrochemical LOHC cycling process had the lowest relative carbon footprint only when highly concentrated LOHCs were used as the feed or when purification of the LOHC product was not required. The carbon footprint in electrochemical cycling of diluted LOHC was primarily contributed to by the LOHC distillation separation process. A sensitivity analysis showed the carbon footprint LOHC concentration dependence during the electrochemical cycling process. Moreover, the electrolyte composition significantly affects the carbon footprint during electrochemical LOHC cycling. Energy utilization, water usage, and toxicity for electrochemical LOHC cycling are discussed to provide an overview for better economic and environmental practices. There are significant opportunities in the electrochemical cycling of LOHCs if appropriate conditions such as high concentrations of reactant, reversible redox cycling ability, high Faradaic efficiencies, and catalyst stabilities are achieved.

Galvanostatic Electroshock Synthesis of Low Loading Au-Pt Nanoalloys Onto Gas Diffusion Electrodes as Multifunctional Electrocatalysts for a Glycerol-Fed Electrolyzer

Water electrolysis is increasingly considered a viable solution for meeting the world's growing energy demands and mitigating environmental issues. An inventive strategy to mitigate the energy requirements involves substituting the energy-intensive oxygen evolution reaction (OER) with biomass-derived glycerol electrooxidation. Nonetheless, the synthesis of electrocatalysts for controlling the selectivity towards added-value chemicals at the anode and efficient H2 generation at the cathode remains a critical bottleneck. Herein, we implemented a galvanostatic electroshock synthesis approach to control the reduction kinetics of Au(III) and Pt(IV) to grow ultra-low amount of gold-platinum alloys on a gas diffusion electrode (12-26 μgmetal cm-2) for glycerol-fed hydroxide anion exchange membrane based electrolyzer. The symmetric GDE-Au100-xPtx||GDE-Au100-xPtx systems showed a notable improvement in electrolyzer performance (GDE-Au64Pt36=201 mA cm-2) as compared to monometallic versions (GDE-Au100Pt0=18 mA cm-2, GDE-Au0Pt100=81 mA cm-2). Chromatography (HPLC) analysis underscores the critical importance of bulk electrolysis methodology (galvanostatic vs potentiostatic) for the efficient conversion of glycerol into high-value-added products. Regarding the electrical energy required to produce 1 kg of H2 for such an electrolyzer fed at the anode with glycerol, our results confirm a drastic decrease by a factor of at least two compared with conventional water electrolysis.

A Two-Dimensional Cu-Based Nanosheet Producing Formic Acid Via Glycerol Electro-Oxidation in Alkaline Water

The sluggishness of the complementary oxygen evolution reaction (OER) is reckoned as one of the major drawbacks in developing an energy-efficient green hydrogen-producing electrolyzer. An array of organic molecule oxidation reactions, operational at a relatively low potential, have been explored as a substitute for the OER. Glycerol oxidation reaction (GOR) has emerged as a leading alternative in this context because glycerol, a waste of biodiesel manufacturing, has become ubiquitous and accessible due to the significant growth in the biodiesel sector in recent decades. Additionally, the GOR generates several value-added organic compounds following oxidation that enhance the cost viability of the overall electrolysis reaction. In this study, a low-cost, room temperature operable, and energy-efficient synthetic methodology has been developed to generate unique two-dimensional CuO nanosheets (CuO NS). This CuO NS material was embedded on a carbon paper electrode, which showcased excellent glycerol electro-oxidation performance operational at a moderately low applied potential. Formic acid is the major product of this CuO NS-driven GOR (Faradaic efficiency ~80 %), as it is formed primarily via the glyceraldehyde oxidation pathway. This CuO NS material was also active for oxidizing other abundant alcohols like ethylene glycol and diethylene glycol, albeit at a relatively poor efficiency. Therefore, this robust CuO NS material has displayed the potential to be used in large-scale electrolyzers functioning with HER/GOR reactions.

Pulse potential mediated selectivity for the electrocatalytic oxidation of glycerol to glyceric acid

Preventing the deactivation of noble metal-based catalysts due to self-oxidation and poisonous adsorption is a significant challenge in organic electro-oxidation. In this study, we employ a pulsed potential electrolysis strategy for the selective electrocatalytic oxidation of glycerol to glyceric acid over a Pt-based catalyst. In situ Fourier-transform infrared spectroscopy, quasi-in situ X-ray photoelectron spectroscopy, and finite element simulations reveal that the pulsed potential could tailor the catalyst's oxidation and surface micro-environment. This prevents the overaccumulation of poisoning intermediate species and frees up active sites for the re-adsorption of OH adsorbate and glycerol. The pulsed potential electrolysis strategy results in a higher glyceric acid selectivity (81.8%) than constant-potential electrocatalysis with 0.7 VRHE (37.8%). This work offers an efficient strategy to mitigate the deactivation of noble metal-based electrocatalysts.

In-situ Bi-modified Pt towards glycerol and formic acid electro-oxidation: Effects of catalyst structure and surface microenvironment on activity and selectivity

The performances of glycerol electro-oxidation reaction (GOR) and formic acid electro-oxidation reaction (FAOR) catalyzed by Pt catalyst were dramatically improved by adding Bi3+ into the reaction solution. The dynamic structure and microenvironment of in-situ Bi-modified Pt and their impact on the catalytic performances were revealed. A strong correlation was established between the Bi coverage of Pt-based catalysts and their resistance to CO poisoning and performance in GOR and FAOR. When Bi3+ increased to a certain amount, a Bi-shell containing hydroxides was formed on Pt surfaces except the formation of Pt-Bi ensemble. On Pt catalyst covered with 43.9 % Bi, the peak mass-specific activities of GOR and FAOR in forward scans were 4.2 and 34.7 times that of Pt/NCNTs, respectively. The peak electrochemical active surface area (ECSA)-specific activity of FAOR in forward scan for Pt with 52.6 % Bi coverage was 80.6 times that of Pt/NCNTs. The dehydrogenation process in FAOR and the 4-electron pathway in GOR were improved for Bi-modified Pt. The experimental results and DFT calculations indicated that the positively charged Bi and structure of Pt-Bi ensemble improved the adsorption and interaction of negatively charged intermediates, and the enhanced hydroxides facilitated the oxidation and removal of toxic intermediates, such as CO.

Coupling Glycerol Conversion with Hydrogen Production Using Alloyed Electrocatalysts

Herein, uniform precious alloys including PtAg, PdAg, and PtPdAg nanoparticles were synthesized as electrocatalysts for glycerol oxidation reaction (GOR). The structures of the samples were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectrometry. The catalytic performance of the samples was evaluated in both alkaline and acidic electrolytes. Among the samples, PtPdAg exhibited superior activity with the largest current density of 3.77 mA cm-2 in alkaline solutions, which is 4.1 and 7.7 times those of Pd/C and Pt/C, respectively. In acidic solutions, the PtPdAg catalyst shows the highest current density of 0.58 mA cm-2, which is 1.8 times that of the Pt/C catalyst. The products of GOR were analyzed by high-performance liquid chromatography. Eight products including oxalic acid, tartronic acid, glyoxylic acid, glyceric acid, glyceraldehyde (GLAD), glycolic acid, lactic acid, and dihydroxyacetone were detected. Notably, in acidic solutions, PtAg and PtPdAg yielded the largest GLAD selectivity of 92.2% at 0.6 and 0.8 V, respectively. Using the alloyed catalysts, electrolysis processes coupling the GOR with the hydrogen evolution reaction were conducted. The conversion of glycerol and production of hydrogen were determined. To highlight the energy efficiency, a solar-panel-powered electrolysis process was conducted for the simultaneous production of hydrogen and high-valued products.

Glycerol Electro-Oxidation in Alkaline Medium with Pt-Fe/C Electrocatalysts Synthesized by the Polyol Method: Increased Selectivity and Activity Provided by Less Expensive Catalysts

We have investigated platinum catalysts containing iron as a modifier to obtain catalysts with superior electrocatalytic activity toward glycerol electro-oxidation in an alkaline medium. The electrocatalysts, supported on carbon Vulcan, were synthesized by the polyol method. The physicochemical characterization data showed that the metals were well distributed on the carbon support and had small particle size (2 nm). The Pt:Fe metal ratio differed from the nominal composition, indicating that reducing iron with platinum was difficult, even though some parameters of the synthesis process were changed. Electrochemical analyses revealed that PtFe/C was more active and stable than commercial Pt/C was, and analysis of the electrolysis by-products showed that iron addition to Pt/C boosted the glycerol conversion and selectivity for glyceric acid formation.

Dihydroxyacetone: A User Guide for a Challenging Bio-Based Synthon

1,3-dihydroxyacetone (DHA) is an underrated bio-based synthon, with a broad range of reactivities. It is produced for the revalorization of glycerol, a major side-product of the growing biodiesel industry. The overwhelming majority of DHA produced worldwide is intended for application as a self-tanning agent in cosmetic formulations. This review provides an overview of the discovery, physical and chemical properties of DHA, and of its industrial production routes from glycerol. Microbial fermentation is the only industrial-scaled route but advances in electrooxidation and aerobic oxidation are also reported. This review focuses on the plurality of reactivities of DHA to help chemists interested in bio-based building blocks see the potential of DHA for this application. The handling of DHA is delicate as it can undergo dimerization as well as isomerization reactions in aqueous solutions at room temperature. DHA can also be involved in further side-reactions, yielding original side-products, as well as compounds of interest. If this peculiar reactivity was harnessed, DHA could help address current sustainability challenges encountered in the synthesis of speciality polymers, ranging from biocompatible polymers to innovative polymers with cutting-edge properties and improved biodegradability.

How to Change the Reaction Chemistry on Nonprecious Metal Oxide Nanostructure Materials for Electrocatalytic Oxidation of Biomass-Derived Glycerol to Renewable Chemicals

Au and Pt are well-known catalysts for electrocatalytic oxidation of biomass-derived glycerol. Although some nonprecious-metal-based materials to replace the costly Au and Pt are used for this reaction, the fundamental question of how the nonprecious catalysts affect the reaction chemistry and mechanism compared to Au and Pt catalysts is still unanswered. In this work, both experimental and computational methods are used to understand how and why the reaction performance and chemistry for the electrocatalytic glycerol oxidation reaction (EGOR) change with electrochemically-synthesized CuCo-oxide, Cu-oxide, and Co-oxide catalysts compared to conventional Au and Pt catalysts. The Au and Pt catalysts generate major glyceric acid and glycolic acid products from the EGOR. Interestingly, the prepared Cu-based oxides produce glycolic acid and formic acid with high selectivity of about 90.0%. This different reaction chemistry is related to the enhanced ability of CC bond cleavage on the Cu-based oxide materials. The density functional theory calculations demonstrate that the formic acids are mainly formed on the Cu-based oxide surfaces rather than in the process of glycolic acid formation in the free energy diagram. This study provides critical scientific insights into developing future nonprecious-based materials for electrochemical biomass conversions.

Predictive control of selective secondary alcohol oxidation of glycerol on NiOOH

Many biomass intermediates are polyols and selectively oxidizing only a primary or secondary alcohol group is beneficial for the valorization of these intermediates. For example, production of 1,3-dihydroxyacetone, a highly valuable oxidation product of glycerol, requires selective secondary alcohol oxidation. However, selective secondary alcohol oxidation is challenging due to its steric disadvantage. This study demonstrates that NiOOH, which oxidizes alcohols via two dehydrogenation mechanisms, hydrogen atom transfer and hydride transfer, can convert glycerol to 1,3-dihydroxyacetone with high selectivity when the conditions are controlled to promote hydrogen atom transfer, favoring secondary alcohol oxidation. This rational production of 1,3-dihydroxyacetone achieved by selectively enabling one desired dehydrogenation pathway, without requiring alteration of catalyst composition, demonstrates how comprehensive mechanistic understanding can enable predictive control over selectivity.

Energy-saving H2 production from a hybrid acid/alkali electrolyzer assisted by anodic glycerol oxidation

Water electrolysis is a promising technology for efficient hydrogen production, but it has been heavily hindered by the sluggish kinetics and high potential of the anodic oxygen evolution reaction (OER). Replacing the OER with the glycerol oxidation reaction (GOR) at the anode is recognized as a potential strategy to address this issue. In this work, the self-supported electrocatalytic electrode of Cu-Cu₂O nanoclusters on carbon cloth (Cu-Cu₂O/CC) is fabricated for the electrocatalysis of the GOR, which has high activity towards the GOR, reaching 10 mA cm^-2 at an applied voltage of 1.21 V, and shows high selectivity for formate production with a faradaic efficiency (FE) of over 80% in a wide potential range. Moreover, a hybrid acid/alkali electrolyzer is assembled by coupling the Cu-Cu₂O/CC anode for the GOR in an alkaline electrolyte with commercial Pt/C as the cathode for the hydrogen evolution reaction (HER) in an acid electrolyte. The dual-electrolyte electrolytic cell only requires an applied voltage of 0.59 V to reach 10 mA cm^-2 with a FE of ∼100% for H₂ and 97% for formate production. This work provides a facile strategy for the application of glycerol upgradation in energy-saving water electrolysis systems.

Direct 3D Printing of Binder-Free Bimetallic Nanomaterials as Integrated Electrodes for Glycerol Oxidation with High Selectivity for Valuable C3 Products

Net-zero carbon strategies and green synthesis methodologies are key to realizing the United Nations' sustainable development goals (SDGs) on a global scale. An electrocatalytic glycerol oxidation reaction (GOR) holds the promise of upcycling excess glycerol from biodiesel production directly into precious hydrocarbon commodities that are worth orders of magnitude more than the glycerol feedstock. Despite years of research on the GOR, the synthesis process of nanoscale electrocatalysts still involves (1) prohibitive heat input, (2) expensive vacuum chambers, and (3) emission of toxic liquid pollutants. In this paper, these knowledge gaps are closed via developing a laser-assisted nanomaterial preparation (LANP) process to fabricate bimetallic nanocatalysts (1) at room temperature, (2) under an ambient atmosphere, and (3) without liquid waste emission. Specifically, PdCu nanoparticles with adjustable Pd:Cu content supported on few-layer graphene can be prepared using this one-step LANP method with performance that can rival state-of-the-art GOR catalysts. Beyond exhibiting high GOR activity, the LANP-fabricated PdCu/C nanomaterials with an optimized Pd:Cu ratio further deliver an exclusive product selectivity of up to 99% for partially oxidized C₃ products with value over 280000-folds that of glycerol. Through DFT calculations and in situ XAS experiments, the synergy between Pd and Cu is found to be responsible for the stability under GOR conditions and preference for C₃ products of LANP PdCu. This dry LANP method is envisioned to afford sustainable production of multimetallic nanoparticles in a continuous fashion as efficient electrocatalysts for other redox reactions with intricate proton-coupled electron transfer steps that are central to the widespread deployment of renewable energy schemes and carbon-neutral technologies.

Promoting biomass electrooxidation via modulating proton and oxygen anion deintercalation in hydroxide

The redox center of transition metal oxides and hydroxides is generally considered to be the metal site. Interestingly, proton and oxygen in the lattice recently are found to be actively involved in the catalytic reactions, and critically determine the reactivity. Herein, taking glycerol electrooxidation reaction as the model reaction, we reveal systematically the impact of proton and oxygen anion (de)intercalation processes on the elementary steps. Combining density functional theory calculations and advanced spectroscopy techniques, we find that doping Co into Ni-hydroxide promotes the deintercalation of proton and oxygen anion from the catalyst surface. The oxygen vacancies formed in NiCo hydroxide during glycerol electrooxidation reaction increase d-band filling on Co sites, facilitating the charge transfer from catalyst surface to cleaved molecules during the 2^nd C-C bond cleavage. Consequently, NiCo hydroxide exhibits enhanced glycerol electrooxidation activity, with a current density of 100 mA/cm² at 1.35 V and a formate selectivity of 94.3%.

Developing catalysts for biomass electrooxidation are critical in electric refinery. The reaction mechanism, however, is still ambiguous. Here, the authors reveal how proton and oxygen anion deintercalation in hydroxide determine the elementary reaction steps in a model reaction of glycerol oxidation.

Selective Photoelectrocatalytic Glycerol Oxidation to Dihydroxyacetone via Enhanced Middle Hydroxyl Adsorption over a Bi2O3-Incorporated Catalyst

Photoelectrocatalytic (PEC) glycerol oxidation offers a sustainable approach to produce dihydroxyacetone (DHA) as a valuable chemical, which can find use in cosmetic, pharmaceutical industries, etc. However, it still suffers from the low selectivity (≤60%) that substantially limits the application. Here, we report the PEC oxidation of glycerol to DHA with a selectivity of 75.4% over a heterogeneous photoanode of Bi₂O₃ nanoparticles on TiO₂ nanorod arrays (Bi₂O₃/TiO₂). The selectivity of DHA can be maintained at ∼65% under a relatively high conversion of glycerol (∼50%). The existing p-n junction between Bi₂O₃ and TiO₂ promotes charge transfer and thus guarantees high photocurrent density. Experimental combined with theoretical studies reveal that Bi₂O₃ prefers to interact with the middle hydroxyl of glycerol that facilitates the selective oxidation of glycerol to DHA. Comprehensive reaction mechanism studies suggest that the reaction follows two parallel pathways, including electrophilic OH* (major) and lattice oxygen (minor) oxidations. Finally, we designed a self-powered PEC system, achieving a DHA productivity of 1.04 mg cm^-2 h^-1 with >70% selectivity and a H₂ productivity of 0.32 mL cm^-2 h^-1. This work may shed light on the potential of PEC strategy for biomass valorization toward value-added products via PEC anode surface engineering.

Electro-Oxidation of Glycerol to High-Value-Added C1-C3 Products by Iron-Substituted Spinel Zinc Cobalt Oxides

Glycerol is a byproduct of biodiesel production and can be a low-cost source for some high-value C1-C3 chemicals. The conversion can be achieved by photo-, thermo-, and electro-catalysis methods. The electrocatalytic oxidation method is attractive due to its moderate reaction conditions and high electron to product efficiency. Most reported catalysts are based on noble metals, while metal oxides are rarely reported. Here, we investigated the electro-oxidation of glycerol on a series of ZnFe_xCo_2-xO₄ (x = 0, 0.4, 1.0, 1.4, and 2.0) spinel oxides. Seven types of value-added C1-C3 products including formate, glycolate, lactate, and glycerate can be obtained by this approach. The selectivity and Faraday efficiency toward these products can be tuned by adjusting the Fe/Co ratio and other experimental parameters, such as the applied potential, glycerol concentration, and electrolyte pH.

Mechanistic Investigations of the Synthesis of Lactic Acid from Glycerol Catalyzed by an Iridium–NHC Complex

In the present work, the reaction pathways and the origin of catalytic activity for the production of lactic acid from glycerol catalyzed by an iridium–heterocyclic carbene (Iridium-NHC) complex at 383.15 K were investigated by DFT study at the M06-D3/6-311++G (d, p)//SDD level. Compared to the noncatalytic reaction pathway, the energy barrier sharply decreased from 75.2 kcal mol−1 to 16.8 kcal mol−1 with the introduction of the iridium–NHC complex. The catalytic reaction pathway catalyzed by the iridium–NHC complex with a coordinated hydroxide included two stages: the dehydrogenation of glycerol to 2,3-dihydroxypropanal, and the subsequent isomerization to lactic acid. Two reaction pathways, including dehydrogenation in terminal and that in C2-H, were studied. It was found that the formation of dihydroxyacetone from the H-removal in C2-H was more favorable, which might have been due to the lower energy of LUMO, whereas dihydroxyacetone could be easily transferred to 2,3-dihydroxypropanal. The analyses of electrostatic potential (ESP), hardness, and f- Fukui function also confirmed that the iridium–NHC complex acted as a hydrogen anion receptor and nucleophilic reaction center to highly promote the conversion of glycerol to lactic acid.

Accelerating Anode Reaction with Electro-oxidation of Alcohols over Ru Nanoparticles to Reduce the Potential for Water Splitting

Generating hydrogen by water electrolysis is a promising and sustainable approach to the production of a green energy carrier, but the sluggish kinetics of the oxygen evolution reaction (OER) at anode leads to a high working potential. Replacing OER with electro-oxidation of organics driven at a low potential offers an effective way to accelerate the sluggish anode reaction, and thus increase hydrogen evolution in water-splitting. Herein, we have prepared a Ru nanoparticles on N-doped carbon nanotubes (Ru-NPs@NCNTs) to implement electro-oxidation of benzyl alcohol toward reducing the anodic potential in watersplitting. The potential of the anode reaction is remarkably decreased from 1.76 to 1.19 V vs RHE at a current density of 10 mA cm^-2 with the assistance of a Ru-NPs catalyst. Furthermore, 100% selectivity and 95% yield of valuable benzaldehyde were achieved simultaneously. The Ru-NPs also exhibits good durability and wide applicability to other alcohols. The high performance of Ru-NPs is mainly attributed to the unique horizontal adsorption configuration of benzyl alcohol with surface atoms of the catalyst, shortening the distance between the ^•OH group and Ru atoms, and increasing the activation rate of the ^•OH group. This work presents a feasible strategy to boost water-splitting performance and concurrently produce value-added organics under mild conditions.

[Pt1Ag37(SAdm)21(Dppp)3Cl6]2+: intercluster transformation and photochemical properties

A novel [Pt1Ag37(SAdm)21(Dppp)3Cl6]2+ nanocluster is reported, and the reaction with PPh3 triggers an intercluster transformation into [Pt1Ag28(SAdm)18(PPh3)4]2+. Using chiral Bdpp, the enantiomeric Pt1Ag37(SAdm)21(R/S-Bdpp)3Cl6 can be prepared.

High activity of NiCo2O4 promoted Pt on three-dimensional graphene-like carbon for glycerol electrooxidation in an alkaline medium

Spinel oxide NiCo₂O₄ supported on a three-dimensional hierarchically porous graphene-like carbon (3D HPG) material has been firstly used to enhance the activity of Pt for glycerol electrooxidation. The addition of NiCo₂O₄ into the Pt/HPG catalyst can significantly improve the catalytic performance for glycerol oxidation. When NiCo₂O₄ is added to the Pt/HPG catalyst, the onset potential is 25 mV more negative than that on the Pt/HPG catalyst without NiCo₂O₄. The current density at -0.3 V on the Pt-NiCo₂O₄ (wt 10 : 1)/HPG electrode is 1.3 times higher than that on the Pt (30 wt%)/HPG electrode. The Pt-NiCo₂O₄ electrode presented in this work shows great potential as an electrocatalyst for glycerol electrooxidation in an alkaline medium.

A review of recent developments on kinetics parameters for glycerol electrochemical conversion - A by-product of biodiesel

Glycerol is a by-product produced from biodiesel, fatty acid, soap and bioethanol industries. Today, the value of glycerol is decreasing in the global market due to glycerol surplus, which primarily resulted from the speedy expansion of biodiesel producers around the world. Numerous studies have proposed ways of managing and treating glycerol, as well as converting it into value-added compounds. The electrochemical conversion method is preferred for this transformation due to its simplicity and hence, it is discussed in detail. Additionally, the factors that could affect the process mechanisms and products distribution in the electrochemical process, including electrodes materials, pH of electrolyte, applied potential, current density, temperature and additives are also thoroughly explained. Value-added compounds that can be produced from the electrochemical conversion of glycerol include glyceraldehyde, dihydroxyacetone, glycolic acid, glyceric acid, lactic acid, 1,2-propanediol, 1,3-propanediol, tartronic acid and mesoxalic acid. These compounds are found to have broad applications in cosmetics, pharmaceutical, food and polymer industries are also described. This review will be devoted to a comprehensive overview of the current scenario in the glycerol electrochemical conversion, the factors affecting the mechanism pathways, reaction rates, product selectivity and yield. Possible outcomes obtained from the process and their benefits to the industries are discussed. The utilization of solid acid catalysts as additives for future studies is also suggested.

Recent advances in the electrooxidation of biomass-based organic molecules for energy, chemicals and hydrogen production

The recent developments in biomass-derivative fuelled electrochemical converters for electricity or hydrogen production together with chemical electrosynthesis have been reviewed.