Glycerol Oxidation Reaction Research Articles

Accelerate oxygen evolution reaction by adding chemical mediator and utilizing solar energy

The electrochemical water splitting to produce clean hydrogen is severely restricted by oxygen evolution reaction (OER) due to the sluggish kinetics of its complicated oxidation process. In this work, the cobalt sulfide nanosheets directly grown on nickel foam (Co–S/Ni3S2@NF) demonstrated an outstanding OER performance with a potential of 1.57 V (vs. RHE) to achieve a current density of 20 mA cm−2, favorably comparing the performance of the noble metal-based catalyst IrO2@NF. The same current density (20 mA cm−2) could be reached at an extremely low potential of 1.35 V (vs. RHE) by adding 0.1 M glycerol, indicating adding chemical mediator is a possible approach to replace the sluggish OER by the corresponding oxidation of chemical mediator. The activation energy comparison of glycerol oxidation reaction (GOR) and OER (21.9 kJ/mol and 28.2 kJ/mol) further proved this conclusion. The solar energy can be captured and utilized to improve OER in the electrochemical water splitting. The anodic current density at ∼1.6 V (vs. RHE) can be increased 10 times by adding glycerol and raising temperature. This work provides solutions to accelerate OER for H2 production.

Role of Ni in PtNi Bimetallic Electrocatalysts for Hydrogen and Value-Added Chemicals Coproduction via Glycerol Electrooxidation.

Pt-based bimetallic electrocatalysts are promising candidates to convert surplus glycerol from the biodiesel industry to value-added chemicals and coproduce hydrogen. It is expected that the nature and content of the elements in the bimetallic catalyst can not only affect the reaction kinetics but also influence the product selectivity, providing a way to increase the yield of the desired products. Hence, in this work, we investigate the electrochemical oxidation of glycerol on a series of PtNi nanoparticles with increasing Ni content using a combination of physicochemical structural analysis, electrochemical measurements, operando spectroscopic techniques, and advanced product characterizations. With a moderate Ni content and a homogenously alloyed bimetallic Pt-Ni structure, the PtNi2 catalyst displayed the highest reaction activity among all materials studied in this work. In situ FTIR data show that PtNi2 can activate the glycerol molecule at a more negative potential (0.4 V RHE) than the other PtNi catalysts. In addition, its surface can effectively catalyze the complete C-C bond cleavage, resulting in lower CO poisoning and higher stability. Operando X-ray absorption spectroscopy and UV-vis spectroscopy suggest that glycerol adsorbs strongly onto surface Ni(OH) x sites, preventing their oxidation and activation of oxygen or hydroxyl from water. As such, we propose that the role of Ni in PtNi toward glycerol oxidation is to tailor the electronic structure of the pure Pt sites rather than a bifunctional mechanism. Our experiments provide guidance for the development of bimetallic catalysts toward highly efficient, selective, and stable glycerol oxidation reactions.

Unrevealing the Correlation between Temperature and Electrocatalytic Activities of Cobalt Sulfide for Oxygen Evolution and Glycerol Oxidation Reactions

The drastic depletion of carbon-based conventional fossil fuels with significant release of greenhouse gases have stimulated research interest towards the development of renewable energy resources. The electrochemical water splitting is considered a promising approach for the sustainable production of clean hydrogen. However, it is severely restricted by oxygen evolution reaction (OER) due to the sluggish kinetics of its complicated oxidation process. Hence, the electrocatalytic performance of OER has a significant impact on the overall water splitting rate and energy efficiency. In this work, we reported two efficient strategies to accelerate OER by adding glycerol as chemical mediator and increasing temperature. The cobalt sulfide nanosheets directly grown on nickel foam (Co-S/Ni3S2@NF) were prepared by hydrothermal method and demonstrated an outstanding OER performance with an overpotential of ~ 340 mV (1.57 V) to achieve a current density of 20 mA cm-2 in alkaline solution, favorably comparing the performance of the noble metal-based catalyst IrO2@NF. This electrocatalyst only requires a potential of ~ 1.35 V to reach the same current density by adding glycerol to the alkaline electrolyte, indicating that glycerol oxidation reaction (GOR) has great potential to replace the sluggish OER. In addition, we found that the OER/GOR electrocatalytic activity increased with increasing temperature. Double current densities for both OER and GOR can be obtained at a potential of 1.60 V when the temperature increased to ~55 oC. This study provides two efficient approaches to overcome the sluggish kinetics of OER and offers new perspectives to improve the energy efficiency for clean hydrogen production.

Electrodeposition of shaped PtIr alloy nanocrystals with high–index facets for the electro–catalytic oxidation of alcohols

Pt–group metal nanocatalysts enclosed with high–index facets have sufficient kink and step atoms on the surface, which could act as efficient sites for fuel cell reactions. Besides surface structure, alloying was another efficient strategy to obtain nanoparticles with excellent catalytic performance. So how about combining the surface structure of high–index facet with alloying to prepare Pt–based nanocatalysts? In this work, we have synthesized alloyed PtIr tetrahexahedral (THH) nanocrystals (NCs) with high–index facets (730) by electrodeposition. And PtIr trioctahedral (TOH) NCs with high–index facets (441) could be obtained by simply decreasing the upper limit potential (EU) of square–wave potential (SWP) with other condition keeping the same as that for the synthesis of PtIr THH NCs. The successful synthesis of alloyed PtIr NCs with high–index facets mainly lied in the repetitive adsorption/desorption of oxygenated species on the surface of nanoparticles. The prepared PtIr THH NCs exhibited excellent electrocatalytic activity and stability towards ethylene glycol oxidation reaction (EGOR) and glycerol oxidation reaction (GOR). Among the nano–catalysts, the peak in the forward scan of PtIr THH NCs for EGOR and GOR were 19.9 mA∙cm−2 and 17.6 mA∙cm−2, respectively, which were 9.5 and 6.8 times higher than those of commercial Pt/C. The excellent electro–catalytic performance of alloyed PtIr NCs could mainly be attributed to the surface structure effect of high–index facets and synergetic effect of the alloy structure. This work could provide a new idea for designing highly efficient nanocatalysts for fuel cells by combing surface structure effect and alloying effect together.

Boosting hydrogen production in ultrathin birnessite nanosheet arrays-based electrolytic cell by glycerol and urea oxidation reactions

It is still a big challenge to develop an innovative strategy to overcome sluggish oxygen evolution reaction (OER). Herein, ultrathin birnessite@nickel foam nanosheet array (KMO@NF) with oxygen vacancy (VO) is prepared by an in-situ growth method. KMO@NF shows a high activity for water splitting because VO and Mn3+ favor the adsorption of OH− and H2O. Furthermore, glycerol oxidation reaction (GOR) and urea oxidation reaction (UOR) are employed to substitute for OER to improve hydrogen evolution reaction (HER). Compared with OER, the anodic current densities of GOR and UOR have increased by 19.34 and 18.04 times at 1.43 V (vs. reverse hydrogen electrode (RHE)), respectively. To reach the same current density of 30 mA/cm2, the required cell voltages for UOR- and GOR-based electrolytic cells have decreased by about 16% than that of water-based electrolytic cell (2.024 V), meaning that to produce the same amount of hydrogen, about 16% of electric energy can be economized. Besides, the Faradaic efficiencies of UOR- and GOR-based electrolytic cells (95% and 97%) are higher than that of water-based electrolytic cell (92%), confirming a higher conversion of energy. The innovative system can not only produce hydrogen efficiently, but also effectively degrade environmental pollutants.

One-step CO assisted synthesis of hierarchical porous PdRuCu nanosheets as advanced bifunctional catalysts for hydrogen evolution and glycerol oxidation

Pd-based catalysts have received wide attention due to their outstanding anti-CO poisoning property, whereas the structural instability limits their application. The hierarchical porous PdRuCu nanosheets (HP PdRuCu NSs) with large electrochemically active surface area, abundant active sites, and stable structures are synthesized through continuous access to CO bubbles. HP PdRuCu NSs exhibit excellent hydrogen evolution reaction (HER) catalytic activity with an ultralow overpotential of 25 mV at 10 mA cm−2 and a Tafel slope of 87.5 mV dec−1 in alkaline·media. Meanwhile, the peak mass activity and specific activity of HP PdRuCu NSs for glycerol oxidation reaction (GOR) are 1083 mA mg−1Pd and 38.8 A m−2, respectively, superior to that of PdRu nanosheets (PdRu NSs), Pd nanosheets (Pd NSs), and commercial Pd black. The introduction of Ru and Cu atoms facilitates the C–C bond cleavage and the complete oxidation of glycerol to CO2, as well as the accelerated oxidation/removal of the poisonous COads in between.

Tailor-designed bimetallic Co/Ni macroporous electrocatalyst for efficient glycerol oxidation and water electrolysis

Water electrolysis is broadly considered one of the most promising technologies for green hydrogen production. However, the oxygen evolution reaction (OER) is thermodynamically unfavorable and requires large overpotentials to proceed with an adequate rate. Herein, we introduce key structural and compositional parameters controlling the hydrogen evolution reaction (HER) performance of a representative family of bimetallic CoNi porous electrocatalysts and highlight a simple strategy for replacing the OER with glycerol oxidation reaction (GOR) to reduce the input cell voltage. The structural, morphological, and electrochemical characterizations of a series of electrocatalysts, prepared by the dynamic hydrogen bubble template technique (DHBT), were fully studied which reveals that changing of Co: Ni ratio affects HER activity. Optimization of this ratio leads to enhancement in both intrinsic and mass activity besides the high density of accessible active sites. This, in turn, leads to an efficient electrocatalyst achieving a low overpotential of −67 mV at a current density of 10 mA/cm2 during HER. As a bifunctional electrocatalyst, it requires only 1.65 V to deliver the same current density with excellent stability for more than 20 h of continuous water electrolysis in alkaline medium. Moreover, the input cell voltage drops by at least 0.2 V during glycerol electrolysis with concurrent production of both hydrogen and value-added chemicals especially hydroxy pyruvate ion.

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.

Ultrahigh Stable Methanol Oxidation Enabled by a High Hydroxyl Concentration on Pt Clusters/MXene Interfaces.

Anchoring platinum catalysts on appropriate supports, e.g., MXenes, is a feasible pathway to achieve a desirable anode for direct methanol fuel cells. The authentic performance of Pt is often hindered by the occupancy and poisoning of active sites, weak interaction between Pt and supports, and the dissolution of Pt. Herein, we construct three-dimensional (3D) crumpled Ti3C2Tx MXene balls with abundant Ti vacancies for Pt confinement via a spray-drying process. The as-prepared Pt clusters/Ti3C2Tx (Ptc/Ti3C2Tx) show enhanced electrocatalytic methanol oxidation reaction (MOR) activity, including a relatively low overpotential, high tolerance to CO poisoning, and ultrahigh stability. Specifically, it achieves a high mass activity of up to 7.32 A mgPt-1, which is the highest value reported to date in Pt-based electrocatalysts, and 42% of the current density is retained on Ptc/Ti3C2Tx even after the 3000 min operative time. In situ spectroscopy and theoretical calculations reveal that an electric field-induced repulsion on the Ptc/Ti3C2Tx interface accelerates the combination of OH- and CO adsorption intermediates (COads) in kinetics and thermodynamics. Besides, this Ptc/Ti3C2Tx also efficiently electrocatalyze ethanol, ethylene glycol, and glycerol oxidation reactions with comparable activity and stability to commercial Pt/C.

Platinum nanoparticles deposited on Cu-doped NiO/C hybrid supports as high-performance catalysts for ethanol and glycerol electrooxidation in alkaline medium

In this work, the influence of Cu-doping on the ability of NiO co-catalyst to enhance the electrocatalytic properties of carbon-supported Pt nanoparticles toward ethanol and glycerol oxidation was investigated. The Cu-doped NiO particles were synthesized by a precipitation method, while the noble metal nanoparticles were deposited over the hybrid Cu-doped NiO/C supports via a pulsed microwave-assisted polyol method using ethylene glycol as reductant. Pt-NiO and Pt-NiOCuO(x:y)/C catalysts with Ni:Cu atomic ratios of 9:1 (Pt-NiOCuO(9:1)/C), 7:3 (Pt-NiOCuO(7:3)/C) and 5:5 (Pt-NiOCuO(5:5)/C) were obtained. The physicochemical analysis showed that the as-prepared catalysts are composed of nanoparticles of about 3 nm. The potentiostatic experiments exhibited that the Pt-NiOCuO(7:3)/C catalyst is the most active catalyst for ethanol oxidation, while the Pt-NiOCuO(5:5)/C catalyst exhibited the best performance for glycerol oxidation. These catalysts developed mass current densities of almost 12 and 5 times higher than those of bare Pt/C for ethanol and glycerol oxidation reactions, respectively. Moreover, an accelerated multicycling stability test displayed that the as-prepared catalysts retain almost 98% of their initial mass current density.

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.

Unveiling the Synergistic Effects of Monodisperse Sea Urchin-like PdPb Alloy Nanodendrites as Stable Electrocatalysts for Ethylene Glycol and Glycerol Oxidation Reactions.

In recent times, the fabrication of noble metal-based catalysts with controllable morphologies has become a research hotspot. Electrocatalytic devices with excellent catalytic performance and enhanced durability for the ethylene glycol oxidation reaction (EGOR) and the glycerol oxidation reaction (GOR) are significant for commercial direct fuel cells. Herein, a series of PdPb sea urchin-like nanodendrite (ND) structures with controllable molar ratios were synthesized as EGOR and GOR electrocatalysts of high efficiency. The optimized structurally regular Pd3Pb NDs exhibit the best electrocatalytic activity and outstanding stability compared to other samples and commercial Pt/C. In addition, the integrated Pb on Pd3Pb NDs can mitigate the bond energy the intermediates generate and further boost the electrooxidation of the intermediates by supplying enough active sites without considering its intrinsic structure, which is beneficial to the enhanced EGOR and GOR activity and stability. With the assistance of electrochemical measurement, the mechanism of the enhanced alloy was further investigated. This paper presents a promising strategy to fabricate catalysts with stable structures, which will elucidate a very promising approach for developing Pd-based catalysts for further applications in fuel cells.

Reactive Distillation of Glycolic Acid Using Heterogeneous Catalysts: Experimental Studies and Process Simulation.

The glycerol oxidation reaction was developed leading to selective catalysts and optimum conditions for the production of carboxylic acids such as glycolic acid. However, carboxylic acids are produced in highly diluted mixtures, challenging the recovery and purification, and resulting in high production costs, polymerization, and thermal degradation of some of the products. The protection of the acid function by esterification reaction is one of the most promising alternatives through reactive distillation (RD); this technique allows simultaneously the recovery of carboxylic acids and the elimination of most part of the water. The reactive distillation, experimental and simulation, of glycolic acid was performed, based on kinetic and thermodynamic models developed. For the thermodynamic model, binary parameters of the missing couples were determined experimentally, and the non-random two-liquid (NRTL) model was selected as the most suitable to represent the binary behavior. The kinetic study of the esterification in the presence of homogeneous and heterogeneous catalysis concluded that the heterogeneous reaction can be accurately described either by a pseudo-homogeneous model or the Langmuir–Hinshelwood (L-H) adsorption model. Reactive distillation was conducted in a distillation column filled with random packing sulfonated ion-exchange resin, Nafion NR50®, or with extruded TiO2-Wox. The conversion rate of glycolic acid in reactive distillation increases from 14% without catalyst to 30% and 36% using Nafion NR50® and TiO2-Wox, respectively. As opposed to the batch reactor study, the conversion rate of glycolic acid was better with TiO2-Wox than with sulfonated ion-exchange resin. The better performance was related to an increase in the hydrodynamics inside the column. Tests using water in the feed confirm the hypothesis by increasing the conversion rate because of the decrease in the mass transfer resistance by reducing the average diffusion coefficient. The simulation of the reactive distillation column with ProSim® Plus showed that the yield of the ester increased operating at a low feed rate with reactive stripping. In the presence of water in the feed, nonreactive stages are required, including an enrichment region to separate water vapor.

Simple Synthesis of PdAg Porous Nanowires as Effective Catalysts for Polyol Oxidation Reaction.

The development of efficient and stable Pd-based electrocatalysts is extremely important to facilitate the development of catalysts for polyol oxidation reactions. To synthesize Pd-based catalysts with excellent catalytic performance, a series of PdAg porous nanowires (PdAg PNWs) with different elemental ratios was constructed by facile synthesis using a seed-mediated method. The synthesized PdAg PNWs have a rough surface and a porous one-dimensional structure, which optimize the specific surface area and surface area of catalysts, thereby providing more active sites for catalysts. PdAg PNWs benefited from the geometric effect of porous nanowires and the synergy between Pd and Ag, showing excellent catalysis (8243.0 and 4137.0 mA mgPd-1) for the ethylene glycol oxidation reaction (EGOR) and glycerol oxidation reaction (GOR). Among them, the optimal Pd62Ag38 PNWs show the highest catalytic activity (6.0 times and 3.9 times higher than Pd/C) and stability compared with Pd57Ag43 PNWs, Pd51Ag49 PNWs, and Pd/C for EGOR and GOR. At the same time, this porous one-dimensional structure also endows PdAg PNWs with faster electron transfer capabilities than Pd/C. This work will likely provide an effective strategy for constructing cost-effective catalysts.

An FTIR Study of the Electrooxidation of C2 and C3 Alcohols on Carbon‐Supported PdxRhy in Alkaline Medium**

AbstractWe have investigated the promoting effect of Rh addition to Pd‐based materials in the electrooxidation of ethanol and glycerol. Physicochemical characterizations (XRD, EDX, TEM, and XPS) of the PdxRhy/C materials, prepared by bromide anion exchange (BAE), showed that the experimental bimetallic compositions were close to the targeted ones. PdxRhy/C particle sizes ranged from 2.2 to 3.8 nm. The ethanol oxidation reaction (EOR) on the PdxRhy/C catalysts yielded four times larger carbonate (CO32−) amount. As for the glycerol oxidation reaction (GOR), the onset potential on the Pd50Rh50/C catalyst occurred at lower potentials. Chromatographic analysis combined with in situ Fourier transform infrared (FTIR) spectroscopy showed that GOR on the Pd50Rh50/C catalyst selectively and quantitatively produced glycerate and tartronate. The outstanding ability of the Pd50Rh50/C catalyst toward EOR and GOR was correlated to the electronic effect expressed by a negative potential shift (200 mV) and the 47 % alloying degree in the Pd50Rh50/C structure.

High C1 selectivity in alkaline ethanol oxidation reaction over stable Lewis pairs of Pd-MxC@CNT (M = W, Mo and Cr)

Pd-based catalysts have been widely studied as electrocatalysts for ethanol oxidation reaction (EOR) because of their higher oxygenophilic properties. However, there are still some disadvantages such as low activity, poor stability and poor selectivity, which hinder the development of EOR. Herein, a method through strong metal-support interaction (SMSI) and heterostructure of Pd-MxC@CNT (M = W, Mo and Cr) to construct a stable Lewis acid-base pair is proposed. Pd-W2C@CNT nanomaterial showed the highest mass activity (13.9 A mgPd−1), C1 selectivity (74.15%) and stability, better than Pd Black (3.5 A mgPd−1, 7.2%) and Pd@CNT (4.1 A mgPd−1, 7.6%). Ex situ and in situ electrochemical experiments reveal that the introduction of W2C became a stable electron donor for Pd, increasing the electron density of Pd atoms and forming a stable Lewis acidity Pd atoms to weaken the adsorption of intermediates. Reducing the electron density of W2C and forming a stable Lewis basicity W2C to provide sufficient OH adspecies for the reaction, thereby increasing the selectivity of the C1 pathway. Furthermore, the Pd-MxC@CNT synthesized by this method also exhibited excellent EOR activity, stability and C1 selectivity and glycerol oxidation reaction (GOR) performance.

Insights on the C2 and C3 electroconversion in alkaline medium on Rh/C catalyst: in situ FTIR spectroscopic and chromatographic studies

The present work evaluates ethanol and glycerol electro-oxidation on Rh/C catalysts prepared using the Bromide Anion Exchange (BAE) method. Physicochemical characterizations were performed using Thermogravimetric Analysis (TGA), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The SPAIRS investigations revealed that the CO adsorption modes on Rh sites occur on the linearly adsorbed CO (COL) and bridged bonded (COB) modes. In ethanol oxidation reaction (EOR), the Rh effect was evaluated by analyzing the products generated after bulk electrolysis using High-Performance Liquid Chromatography (HPLC) and in situ FTIR spectroscopy. The results confirmed the C-C cleavage Rh ability at low potentials and revealed that EOR follows both reaction pathways on Rh/C. While in glycerol oxidation reaction (GOR), Rh addition increases high added-value products formation such as glycerate ion. The GOR main route follows the glyceraldehyde pathway. The results highlighted that Rh is a good candidate for ethanol and glycerol electrochemical conversion at low potentials.

Paired formate and H2 productions via efficient bifunctional Ni-Mo nitride nanowire electrocatalysts

Electrocatalytic water splitting provides a potentially sustainable approach for hydrogen production, but is typically restrained by kinetically slow anodic oxygen evolution reaction (OER) which is of lesser value. Here, free-standing, hetero-structured Ni3N-Ni0.2Mo0.8N nanowire arrays are prepared on carbon cloth (CC) electrodes for hydrogen evolution reaction (HER) and glycerol oxidation reaction (GOR) to formate with a remarkably high Faradaic efficiency of 96%. A two-electrode electrolyzer for GOR-assisted hydrogen production operates with a current density of 10 mA cm−2 at an applied cell voltage of 1.40 V, 220 mV lower than for alkaline water splitting. In-situ Raman measurements identify Ni (III) as the active form of the catalyst for GOR rather than Ni (IV) and in-situ Fourier transform infrared (FTIR) spectroscopy measurements reveal pathways for GOR to formate. From density functional theory (DFT) calculations, the Ni3N-Ni0.2Mo0.8N heterostructure is beneficial for optimizing adsorption energies of reagents and intermediates and for promoting HER and GOR activities by charge redistribution across the heterointerface. The same electrode also catalyzes conversion of ethylene glycol from polyethylene terephthalate (PET) plastic hydrolysate into formate. The combined results show that electrolytic H2 and formate production from alkaline glycerol and ethylene glycol solutions provide a promising strategy as a cost-effective energy supply.

Aerosol‐Based Synthesis of Multi‐metal Electrocatalysts for Oxygen Evolution and Glycerol Oxidation

AbstractDiscovery of new catalysts is crucial for future growth and development of environmentally friendly energy conversion processes e. g. the production of hydrogen by water electrolysis. We developed an aerosol‐based synthesis technique as a comparatively fast and facile method to prepare multi‐metal catalysts. 22 different quinary metal compositions were synthesized and investigated with respect to their activity for the oxygen evolution (OER) and the glycerol oxidation (GOR) reactions. The impact of the element composition and the homogeneous distribution of the elements in the particles on catalytic performance were evaluated. The highest activity for OER was found for Co20Cu20Ni20Fe20Zn20. For GOR, Ag‐containing catalysts were the most active, however, in most cases Ag was locally enriched and not homogeneously mixed with the other metals in the particles. Ag‐based catalysts outperformed similar compositions containing one or more noble metals. The GOR selectivity of selected catalysts during long‐term electrolysis was also investigated and it was shown that varying the catalyst composition via aerosol‐based synthesis is a potential way to modulate the GOR selectivity.

Bifunctional Mn-doped CoSe2 nanonetworks electrode for hybrid alkali/acid electrolytic H2 generation and glycerol upgrading

Electrolytic water splitting, as a promising route to hydrogen (H2) production, is still confronted with the sluggish anodic oxygen evolution reaction (OER) and its less value-added O2 production. Herein, we report a bifunctional electrode fabricated by in situ growth of Mn-doped CoSe2 nanonetworks on carbon fiber cloth (Mn-CoSe2/CFC), which shows attractive electrocatalytic properties toward glycerol oxidation reaction (GOR) in alkali and hydrogen evolution reaction (HER) in acid. A flow alkali/acid hybrid electrolytic cell (fA/A-hEC) was then developed by coupling anodic GOR with cathodic HER with the Mn-CoSe2/CFC bifunctional electrode. Such fA/A-hEC enables a rather low voltage of 0.54 V to achieve 10 mA cm−2, and maintain long-term electrolysis stability over 300-h operation at 100 mA cm−2 with Faraday efficiencies of over 99% for H2 and 90% for formate production. The designed bifunctional electrode in such innovative fA/A-hEC device provides insightful guidance for coupling energy-efficient hydrogen production with biomass upgradation.