Activity For Glycerol Oxidation Reaction Research Articles

Metal‐Phthalocyanine‐Based Two‐Dimensional Conjugated Metal‐Organic Frameworks for Electrochemical Glycerol Oxidation Reaction

Electrochemical glycerol oxidation reaction (GOR) is a promising candidate to couple with cathodic reaction, like hydrogen evolution reaction, to produce high‐value product with less energy consumption. Two‐dimensional conjugated metal‐organic frameworks (2D c‐MOFs), comprising square‐planar metal‐coordination motifs (e.g., MO4, M(NH)4, MS4), are notable for their programable active sites, intrinsic charge transport, and excellent stability, making them promising catalyst candidates for GOR. Here, we introduce a novel class of 2D c‐MOFs electrocatalysts, M2[NiPcS8] (M=Co/Ni/Cu), which are synthesized via coordination of octathiolphthalocyaninato nickel (NiPc(SH)8) with various metal centers. Due to a fast kinetic and high activity of CoS4 sites for GOR, the electrocatalytic tests demonstrate that Co2[NiPcS8] supported on carbon paper displays a low GOR potential of 1.35 V vs. RHE at 10 mA cm‐2, significantly reducing the overall water‐electrolysis‐voltage reduction by 0.27 V from oxygen evolution reaction to GOR, thereby outperforming Ni2[NiPcS8] and Cu2[NiPcS8]. Additionally, we have determined that the GOR activity of CoX4 linkage sites varies with different heteroatoms, following an experimentally and theoretically confirmed activity order of CoS4>CoO4>Co(NH)4. The GOR performance of Co2[NiPcS8] not only demonstrate superior performance among non‐noble metal complex, but also provides critical insights on designing high‐performance MOF electrocatalysts upon optimizing the electronic environment of active sites.

Metal‐Phthalocyanine‐Based Two‐Dimensional Conjugated Metal‐Organic Frameworks for Electrochemical Glycerol Oxidation Reaction

Electrochemical glycerol oxidation reaction (GOR) is a promising candidate to couple with cathodic reaction, like hydrogen evolution reaction, to produce high‐value product with less energy consumption. Two‐dimensional conjugated metal‐organic frameworks (2D c‐MOFs), comprising square‐planar metal‐coordination motifs (e.g., MO4, M(NH)4, MS4), are notable for their programable active sites, intrinsic charge transport, and excellent stability, making them promising catalyst candidates for GOR. Here, we introduce a novel class of 2D c‐MOFs electrocatalysts, M2[NiPcS8] (M=Co/Ni/Cu), which are synthesized via coordination of octathiolphthalocyaninato nickel (NiPc(SH)8) with various metal centers. Due to a fast kinetic and high activity of CoS4 sites for GOR, the electrocatalytic tests demonstrate that Co2[NiPcS8] supported on carbon paper displays a low GOR potential of 1.35 V vs. RHE at 10 mA cm‐2, significantly reducing the overall water‐electrolysis‐voltage reduction by 0.27 V from oxygen evolution reaction to GOR, thereby outperforming Ni2[NiPcS8] and Cu2[NiPcS8]. Additionally, we have determined that the GOR activity of CoX4 linkage sites varies with different heteroatoms, following an experimentally and theoretically confirmed activity order of CoS4>CoO4>Co(NH)4. The GOR performance of Co2[NiPcS8] not only demonstrate superior performance among non‐noble metal complex, but also provides critical insights on designing high‐performance MOF electrocatalysts upon optimizing the electronic environment of active sites.

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.

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.

PtSb/C electrocatalysts for glycerol oxidation in alkaline electrolyte

Pt/C and PtSb/C catalysts in various atomic ratios were synthesized by the sodium borohydride reducing method and their activity for the glycerol oxidation reaction (GOR) was evaluated in alkaline media. Transmission Electron Microscopy (TEM) images showed that Pt particle size increases with increasing Sb content in the catalyst. X-ray photoelectron spectroscopy (XPS) showed that the ratio of Pt and Sb is close to that expected. By XPS measurements, the presence of Sb2O5 in Pt70Sb30/C and Pt50Sb50/C was observed. X-ray diffraction (XRD) analysis revealed the presence of the face-centered cubic (FCC) structure of Pt and PtSb and of some others phases that could be identified as Sb oxides. By linear sweep voltammetry (LSV) measurements, Pt80Sb20/C showed the highest activity for the GOR in alkaline media for potentials >−0.35 V vs. Ag/AgCl, while Pt50Sb50/C showed the highest GOR activity in the potential range between −0.60 and −0.35 V vs. Ag/AgCl. The direct glycerol fuel cells with Pt80Sb20/C as the anode catalyst showed the best performance. These results attest the beneficial effect of Sb addition to platinum: the activity enhancement in the presence of Sb atoms has to be ascribed to both a bifunctional mechanism related to the presence of Sb oxides, and an electronic effect between platinum and antimony in the PtSb alloy.

Electrocatalytic Oxidation of Glycerol Using Solid‐State Synthesised Nickel Boride: Impact of Key Electrolysis Parameters on Product Selectivity

AbstractWater electrolysis is a promising technology for sustainable hydrogen production; however, its commercialisation is limited by sluggish kinetics of the oxygen evolution reaction (OER). A potential alternative to the OER is hence required and is seen in the electrocatalytic glycerol oxidation reaction (GOR) as it offers concomitant value‐added product generation from a cheap and abundant feedstock. Here, we show a facile solid‐state synthesis method to obtain Ni‐boride, a non‐noble metal‐based catalyst subsequently used in an in‐depth study of the GOR product distribution as a function of key electrolysis parameters. Highly crystalline, mixed‐phase Ni borides were obtained, and their synthesis was successfully optimised regarding GOR activity. Long‐term chronoamperometry was conducted in a circular flow‐through cell and samples were analysed by HPLC. It is shown that the formation of lactic acid, one of the most valuable GOR products, can be enhanced by optimising the electrolyte composition and the applied potential.

Boosting the electrocatalytic glycerol oxidation performance with highly-dispersed Pt nanoclusters loaded on 3D graphene-like microporous carbon

Preparing Pt nanostructure catalysts with better support materials is an efficient catalyst design strategy to develop high performance Pt-based electrocatalysts. Here we report for the first time a method to synthesize highly-dispersed Pt nanoclusters supported on microporous three-dimensional (3D) graphene-like carbon (3D-GLC) for use in the electrochemical oxidation reaction. The Pt nanoclusters loaded on 3D graphene-like carbon (Pt/3D-GLC) are synthesized by Ca2+-exchanged beta zeolite template based carbon synthesis and subsequent Pt impregnation methods. Highly-dispersed Pt nanoclusters (ca. 1.25 ± 0.30 nm) loaded on the 3D-GLC having a large surface area (ca. 2910 m2/g) demonstrate superior electrocatalytic performance for electrochemical glycerol oxidation reaction (GOR) over that of a commercial Pt/C catalyst. We hypothesize in this work that the improved GOR performance of Pt/3D-GLC is related to the increase of Pt active sites by decreasing Pt cluster size and the change in the physicochemical properties of the Pt by interaction between the Pt cluster and 3D-GLC. In addition, first-principle density functional theory (DFT) and ab-initio molecular dynamics (MD) simulations are performed to demonstrate that the finely-dispersed Pt nanoclusters on 3D-GLC support can give rise to excellent GOR activity in accordance with the enhanced adsorption behavior of glycerol on its Pt crystal surfaces.

Mechanism of glycerol oxidation reaction on silver-modified palladium electrode in alkaline medium

The silver-modified Pd (Ag/Pd) electrode was prepared by underpotential deposition of Cu adatoms, followed by galvanic displacement with Ag atoms to investigate the effect of silver modification on the catalysis and mechanism for glycerol oxidation reaction (GOR) of Pd. Cyclic voltammograms in alkaline glycerol solution exhibited that the Ag/Pd electrode had ca. 100 mV less positive onset potential of the GOR current density and higher peak current density than the Pd electrode, indicating that the GOR activity of Pd was enhanced by surface modification with Ag atoms. In potentiostatic electrolysis at −0.1 V vs. Hg/HgO, GOR mainly began with the oxidation of a terminal OH group for both electrodes, and glycerate and glycolate were major products. The glycolate production was more active for the Ag/Pd electrode. The in situ infrared reflectance-absorption spectra (IRAS) exhibited that GOR products with one or two carbons were detected at lower potentials for the Ag/Pd electrode, indicating that the CC bond cleavage was facilitated by the Ag modification.

Performance of Pd Electrocatalyst Supported on a Physical Mixture Indium Tin Oxide–carbon for Glycerol Electro–oxidation in Alkaline Media

AbstractPalladium electrocatalysts, supported on Vulcan XC 72 carbon and indium tin oxide (ITO) with different ratios, were prepared by borohydride reduction method and analysed for glycerol electro‐oxidation application in the presence of KOH solution. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) techniques were used to characterize the particle size and crystal electrocatalyst structures, whereas their catalytic activities regarding the glycerol electro‐oxidation were evaluated by cyclic voltammetry (CV), chronoamperometry and tested in a direct alkaline glycerol fuel cell (DGFC) by electrochemical techniques. Micrographs results showed that the ITO presence promotes a large agglomeration of particles. Pd/C–ITO electrocatalysts showed peaks associated with the face‐centered cubic (fcc) structure of palladium and several others peaks associated with ITO used as support. Similar performance was found on all Pd/C–ITO electrocatalysts where measurements in CV were compared to Pd/C and Pd/ITO with Pd/C–ITO 50:50 chronoamperometry, presenting a better performance for glycerol electro‐oxidation. When using Pd/C–ITO 85:15 electrocatalyst and 1.0 mol L−1 glycerol at 90 °C, the maximum power density found was 2,1 times higher than that obtained using Pd/C and Pd/CITO electrocatalysts. Therefore, the physical mixture of ITO and carbon, to be used as a support improves the electrocatalytic activity for glycerol oxidation reaction.

Effect of Silver Modification on Glycerol Oxidation Reaction Activity of Palladium Electrode in Alkaline Medium

Introduction Biodiesel fuel (BDF) attracts attention as a carbon-neutral fuel as well as bioethanol. As the production of BDF increases, the production of the glycerol byproduct is also increasing. It is important to develop new uses for glycerol to cope with the mass production of BDF. The use of glycerol as a fuel for direct alcohol fuel cells is promising, because anodic oxidation of glycerol produced by bioprocesses occurs in carbon-neutral cycles and direct glycerol fuel cells are expected to produce electricity with a low environmental load and to be energy efficient. It is well-known that Pd is cheaper than Pt and Au, and Pd-based alloy electrodes are highly active for the oxidation of alcohols in alkaline media. We also have reported the PdAg alloys-loaded carbon exhibited higher glycerol oxidation reaction (GOR) activity and tolerance to poisoning species than Pd.1 The mechanism for GOR, however, is not so clear. In this study we prepared an Ag atomic layer-modified Pd model electrode, and investigated the potential dependence of GOR products by in situ infrared reflectance-absorption spectroscopy (IRAS). In addition, we discussed the GOR mechanism based on these data. Experimental The Ag atomic layer-loaded Pd (Ag/Pd) electrode was prepared by underpotential deposition of Cu (Cu-upd) on a Pt polycrystalline substrate and the following galvanic replacement with Ag. The coverage of Ag (θ Ag) on the Pd substrate was evaluated to be 0.5 from the charges for Cu-upd before and after the Ag modification. 1 M KOH and (1 M KOH + 0.5 M glycerol) solution were used for electrochemical measurements. In situ infrared reflection-absorption spectroscopy (IRAS) was used to qualitatively analyze the products of GOR on the Pd and Ag/Pd electrodes in alkaline solution. All electrochemical measurements were performed at room temperature. Results and Discussion The cyclic voltammograms of the Pd and Ag/Pd electrodes in a (1 M KOH + 0.5 M glycerol) solution is shown in Fig. 1. The Ag/Pd electrode had higher oxidation current and more negative onset potential of the oxidation current than the Pd electrode, clearly indicating that the GOR activity was enhanced by the modification of the Ag atomic layer. In addition, the peak potential of the oxidation current for the Ag/Pd electrode was more positive than that for the Pd electrode, suggesting that the former was superior in tolerance to poisoning species to the latter. IRAS spectra for the Pt electrode exhibited that the absorption peak at 1335 cm-1 assigned to the formation of dihydroxyacetone was mainly increased at lower potentials, but the absorption peak at 1310 cm-1 assigned to the formation of glycerate was increased at higher potentials. This suggests that the secondary OH group in a glycerol molecule is preferentially oxidized at smaller overpotentials, and the primary OH group is greatly oxidized at larger overpotentials. For the Ag/Pd electrode, the oxidation of the primary OH group occurred even at smaller overpotentials, and hydroxypyruvate was also formed at larger overpotentials. Acknowledgement This work was partially supported by JSPS KAKENHI Grant Number 15H04162. Reference 1 B. T. X. Lam, M. Chiku, E. Higuchi, H. Inoue, J. Power Sources, 297, 149 (2015). Figure 1

Glycerol Oxidation Reaction Mechanism on Ag-Modified Pt Electrode in Alkaline Medium

Introduction Recently, biodiesel fuel (BDF) attracts attention due to the progress of global warming. Glycerol as a byproduct is produced with BDF, and practically used for pharmaceuticals, cosmetics, food additives and so on. With the mass production of BDF, new applications of the glycerol byproduct need to be found. The application of glycerol as anode for direct alcohol fuel cells (DAFCs) can be an important solution because it has low toxicity and high specific energy (5.0 kWh kg-1). However, glycerol has two C-C bonds and three OH groups, so the mechanism for glycerol oxidation reaction (GOR) is complex,1 and the rate for GOR is so slow that the complete oxidation to CO2 is very difficult. Palladium is known to be one of active materials for GOR. We have found the alloy nanoparticles of Pd with Ag or Au improved the GOR activity and tolerance to the poisoning species on Pd nanoparticle in alkaline medium due to the electronic and bi-functional effects.2 Meanwhile, the Pt electrode had higher GOR activity than the Pd electrode in terms of the onset potential of GOR current, and Ag would improve the GOR activity of Pt. In this study, the effect of the modification with Ag on the GOR activity of a Pt substrate was evaluated by cyclic voltammetry (CV). Moreover, the mechanism for GOR on the Ag-modified Pt (Ag/Pt) electrode was discussed based on in situ infrared reflection absorption spectra at different potentials. Experimental The Ag/Pt electrode was prepared by underpotential deposition of Cu (Cu-upd) on a Pt substrate and the following galvanic replacement with Ag. The coverage of Ag (θ Ag) on the Pt substrate were calculated from the charge for H desorption before and after the Ag modification. The Ag/Pt electrodes with θ Ag = 0.8 and 0.5 were used in this study, which are denoted as Ag(0.8)/Pt and Ag(0.5)/Pt, respectively. The electrolytes were 1 M KOH or (1 M KOH + 0.5 M glycerol) solutions. Pt plate (1 cm × 1 cm) and a Hg/HgO electrode were used as counter and reference electrodes, respectively. In situ infrared reflection-absorption spectroscopy (IRAS) was used to qualitatively analyze the products of GOR on the Pt, Ag(0.8)/Pt and Ag(0.5)/Pt electrodes in alkaline solution. All electrochemical measurements were performed at room temperature. Results and Discussion The GOR activity for the Pt, Ag(0.8)/Pt and Ag(0.5)/Pt electrodes in alkaline medium was evaluated by CV (Fig. 1). Both Ag(0.8)/Pt and Ag(0.5)/Pt electrodes had twice higher current density and about 150 mV lower onset potential than the Pt substrate. This means that the enhancement of the GOR activity is caused by the modification of Ag atomic layers. Moreover, as θ Ag increased, a GOR wave was separated into two. The durability for GOR was evaluated by potentiostatic electrolysis for 60 min at -0.1 V and -0.3 V (vs. Hg/HgO). At -0.1 V, the durability for GOR was decreased in the order of Ag(0.5)/Pt > Pt > Ag(0.8)/Pt. On the other hand, at -0.3 V, the Ag(0.5)/Pt electrode still showed the best tolerance to the poisoning species, but the durability for GOR of Ag(0.5)/Pt was poorer than that of Pt. These results indicated that the modification of Ag on Pt improved the GOR activity and durability. IRAS gives us the information on the GOR mechanism. In the case of the Pt electrode, the mainly absorption band are observed at 1310 cm-1, 1335 cm-1, 1350 cm-1, 1385 cm-1 and 1575 cm-1 which can be attributed to glyceraldehyde or glycerate, dihydroxyacetone, hydroxypyruvate, symmetric and symmetric O-C-O stretching of carboxylate, respectively. At higher potentials, the absorption band at 1310 cm-1 was obviously observed. On the other hand, in the case of both Ag(0.8)/Pt and Ag(0.5)/Pt electrodes, the absorption band at 1335 cm-1 due to dihydroxyacetone was more obviously observed at -0.4 to -0.2 V, whereas at -0.2 to 0.1 V, the absorption band at 1310 and 1350 cm-1 was strengthen. This results indicate that the oxidation of primary and secondary OH groups depends on potential, and the secondary OH (-0.4 to -0.2 V) and the primary OH ( -0.1 V) are preferentially oxidized on the Ag modified Pt electrodes. Acknowledgement This work was partially supported by JSPS KAKENHI Grant Number 15H04162. References 1) M. Simoes et al., Appl. Catal. B: Environ., 93, 354 (2010).2) B. T. X. Lam et al., J. Power Sources, 297, 149 (2015). Figure 1

PtAg Nanoparticle Electrocatalysts for the Glycerol Oxidation Reaction in Alkaline Medium

To improve the activity for glycerol oxidation reaction (GOR) of Pt, PtAg (mole ratio of Pt/Ag = 3 and 1) alloy nanoparticle-loaded carbon black (Pt/CB, PtAg(3:1)/CB, PtAg(1:1)/CB) catalysts were prepared by a wet method. The resultant catalysts, moreover, were heat-treated in a N2 atmosphere at 200°C. The alloying of Pt with Ag for each PtAg/CB was confirmed by X-ray diffractometry and electron dispersive X-ray spectrometry. The heat-treatment did not change the crystal structure of the PtAg alloys and increased their particle size. X-ray photoelectron spectroscopy exhibited that stabilizers were completely removed from the PtAg alloy surface, and the Pt4f and Ag3d doublets due to metallic Pt and Ag, respectively, shifted to lower binding energies, supporting the alloying of Pt with Ag. Both PtAg/CB electrodes had two oxidation waves of glycerol irrespective of heat-treatment, which was different from the Pt/CB electrode. The onset potential of the first oxidation wave was -0.60 V, which was 0.20 V less positive than that for the Pt/CB electrode, indicating the alloying of Pt with Ag greatly improved the GOR activity of Pt. The heat-treated PtAg(3:1)/ CB electrode improved the GOR current density of the second oxidation peak. In the potentiostatic electrolysis at -0.1 and 0 V for both PtAg/CB electrodes, the ratio of oxidation current density at 60 min to that at 5 min (j60/j5), an indicator of the catalyst deterioration, at 0 V was higher than that at -0.1 V, because the adsorbed oxidation intermediates were greatly consumed at the larger overpotential. The heat-treatment of the PtAg(3:1)/CB electrode increased the j60/j5 value at -0.1 V but decreased that at 0 V. This could be attributed to the formation of high-order oxidation intermediates which might have stronger poisoning effect.

Rhodium Nanoparticle-Loaded Carbon Black Electrocatalyst for the Glycerol Oxidation Reaction in Alkaline Medium

Rhodium nanoparticle-loaded carbon black (Rh/CB) was prepared by a wet method, and its activity and durability for glycerol oxidation reaction (GOR) in alkaline medium were compared with Pt, Pd and Au nanoparticle-loaded CB (Pt/CB, Pd/CB and Au/CB). In the cyclic voltammogram of the Rh/CB electrode, the redox waves due to hydrogen adsorption/desorption and the surface OH monolayer formation/reduction were observed at more negative potentials than the Pt/CB and Pd/CB electrodes. The onset and peak potentials of the GOR current densities for the Rh/CB electrode were ca. –0.55 and –0.30 V vs. Hg/HgO, respectively, which were 0.10 and 0.20 V more negative than the Pt/CB electrode whose GOR activity was the best, indicating that Rh was a fascinating metal for reducing the overpotential for GOR. In the electrostatic electrolysis with the Rh/CB and Pt/CB electrodes, the decrease in the GOR current density in the former with time was suppressed compared to that in the latter, suggesting that the tolerance to poisoning for the Rh/CB electrode was superior to that for the Pt/CB electrode.

Simple polyol synthesis of porous coral-like palladium–silver alloy nanostructures with enhanced electrocatalytic activity for glycerol oxidation reaction

A simple and facile one-pot polyol method was developed for the synthesis of porous Pd63Ag37 alloy coral-like nanostructures, which exhibited improved electrocatalytic activity and enhanced stability for glycerol oxidation reaction.