On the mechanism of ethanol electro-oxidation on Pt and PtSn catalysts: electrochemical and in situ IR reflectance spectroscopy studies

Photothermal CO2 conversion to ethanol through photothermal heterojunction-nanosheet arrays

Photothermal CO2 conversion to ethanol offers a sustainable solution for achieving net-zero carbon management. However, serious carrier recombination and high C-C coupling energy barrier cause poor performance in ethanol generation. Here, we report a Cu/Cu2Se-Cu2O heterojunction-nanosheet array, showcasing a good ethanol yield under visible-near-infrared light without external heating. The Z-scheme Cu2Se-Cu2O heterostructure provides spatially separated sites for CO2 reduction and water oxidation with boosted carrier transport efficiency. The microreactors induced by Cu2Se nanosheets improve the local concentration of intermediates (CH3* and CO*), thereby promoting C-C coupling process. Photothermal effect of Cu2Se nanosheets elevates system's temperature to around 200 °C. Through synergizing electron and heat flows, we achieve an ethanol generation rate of 149.45 µmol g-1 h-1, with an electron selectivity of 48.75% and an apparent quantum yield of 0.286%. Our work can serve as inspiration for developing photothermal catalysts for CO2 conversion into multi-carbon chemicals using solar energy.

Titanium Oxycarbide as Platinum-Free Electrocatalyst for Ethanol Oxidation

The compound material titanium oxycarbide (TiOC) is found to be an effective electrocatalyst for the electrochemical oxidation of ethanol to CO2. The complete course of this reaction is one of the main challenges in direct ethanol fuel cells (DEFCs). While TiOC has previously been investigated as catalyst support material only, in this study we show that TiOC alone is able to oxidize ethanol to acetaldehyde without the need of expensive noble metal catalysts like Pt. It is suggested that this behavior is attributed to the presence of both undercoordinated sites, which allow ethanol to adsorb, and oxygenated sites, which facilitate the activation of water. This is a milestone in DEFC research and development and opens up innovative possibilities for the design of catalyst materials for intermediate temperature fuel cells.

Au/Pt Bimetallic Nanowires with Stepped Pt Sites for Enhanced C-C Cleavage in C2+ Alcohol Electro-oxidation Reactions

Efficient C-C bond cleavage and oxidation of alcohols to CO2 is the key to developing highly efficient alcohol fuel cells for renewable energy applications. In this work, we report the synthesis of core/shell Au/Pt nanowires (NWs) with stepped Pt clusters deposited along the ultrathin (2.3 nm) stepped Au NWs as an active catalyst to effectively oxidize alcohols to CO2. The catalytic oxidation reaction is dependent on the Au/Pt ratios, and the Au1.0/Pt0.2 NWs have the largest percentage (∼75%) of stepped Au/Pt sites and show the highest activity for ethanol electro-oxidation, reaching an unprecedented 196.9 A/mgPt (32.5 A/mgPt+Au). This NW catalyst is also active in catalyzing the oxidation of other primary alcohols, such as methanol, n-propanol, and ethylene glycol. In situ X-ray absorption spectroscopy and infrared spectroscopy are used to characterize the catalyst structure and to identify key reaction intermediates, providing concrete evidence that the synergy between the low-coordinated Pt sites and the stepped Au NWs is essential to catalyze the alcohol oxidation reaction, which is further supported by DFT calculations that the C-C bond cleavage is indeed enhanced on the undercoordinated Pt-Au surface. Our study provides important evidence that a core/shell structure with stepped core/shell sites is essential to enhance electrochemical oxidation of alcohols and will also be central to understanding electro-oxidation reactions and to the future development of highly efficient direct alcohol fuel cells for renewable energy applications.

Research on UO2 modification of a direct ethanol fuel cell Pt/C catalyst

Radioactive UO2 powder was prepared by hydrothermal method and a set of Pt-xUO2/C catalysts were synthesized by impregnation method for solving the problem of low activity and easy poisoning of anode Pt/C catalysts for a direct ethanol fuel cell. XRD, TEM, EDS, XPS and ICP-MS characterization showed the successful loading of Pt and UO2 onto the carbon carrier. Electrochemical workstation and single cell test results confirm that the catalytic performance of Pt-10% UO2/C is significantly better than Pt/C-eg. It is speculated that the synergistic effect of Pt and U enhances the catalytic activity and UO2 improves the resistance to CO poisoning by releasing O2 stored in the lattice space, while the α-particles released by 235U can also generate radiolysis product OH and promote the oxidative desorption of CO from the Pt surface.

Quantitative Evaluation of Carrier Dynamics in Full-Spectrum Responsive Metallic ZnIn2S4 with Indium Vacancies for Boosting Photocatalytic CO2 Reduction

The influence of defects on quantitative carrier dynamics is still unclear. Therefore, full-spectrum responsive metallic ZnIn₂S₄ (V_In-rich-ZIS) rich in indium vacancies and exhibiting high CO₂ photoreduction efficiency was synthesized for the first time. The influence of the defects on the carrier dynamic parameters was studied quantitatively; the results showed that the minority carrier diffusion length (L_D) is closely related to the catalytic performance. In situ infrared spectroscopy and theoretical calculations revealed that the presence of indium vacancies lowers the energy barrier for CO₂ to CO conversion via the COOH* intermediate. Hence, the high rate of CO evolution reaches 298.0 μmol g^-1 h^-1, a nearly 28-fold enhancement over that with ZnIn₂S₄ (V_In-poor-ZIS), which is not rich in indium vacancies. This work fills the gaps between the catalytic performance of defective photocatalysts and their carrier dynamics and may offer valuable insight for understanding the mechanism of photocatalysis and designing more efficient defective photocatalysts.

Electro-Catalytic Properties of Palladium and Palladium Alloy Electro-Catalysts Supported on Carbon Nanofibers for Electro-Oxidation of Methanol and Ethanol in Alkaline Medium

Carbon nanofibers (CNFs) supported by Pd and Pd-Sn electro-catalysts were prepared by the chemical reduction method using ethylene glycol as the reducing agent. Their physicochemical characteristics were studied using high resolution-transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Bruanaer-Emmett-Teller (BET) analysis. FTIR revealed that oxygen, hydroxyl, carboxylic and carbonyl functional groups facilitated the dispersion of Pd and Sn nanoparticles. The doping of Pd with Sn to generate PdSn alloy was also confirmed by XPS data. The amorphous nature of CNFs was confirmed by XRD patterns which exhibited the Pd diffraction peaks. When Sn was added to Pd/CNFs, the diffraction peaks moved to lower angles. HRTEM images revealed that the CNFs with cylindrical shape-like morphology and also Pd-Sn nanoparticles dispersed on carbon support. The catalytic activity and stability towards alcohol electro-oxidation in alkaline medium at room temperature was evaluated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The obtained Pd-Sn/CNFs electro-catalyst exhibited a better electro-catalytic activity than Pd/CNFs and Pd/C electro-catalysts for both methanol and ethanol oxidation. The improvement of the electrochemical performance was associated with the synergistic effect via the addition of Sn which modified the Pd atom arrangement, thereby promoting oxidation through a dehydrogenation pathway. Furthermore, SnO2 generates abundant OH species which helps with increasing the rate of the oxidative removal of carbon monoxide (CO) intermediates from Pd sites.

In-Situ surface enhanced infrared absorption spectroscopy study of electrocatalytic oxidation of ethanol on Platinum/Gold surface

The behavior of ethanol oxidation reaction on composite electrodes prepared by deposition platinum on a gold surface (Pt/Au) were studied by cyclic voltammetry and surface enhanced infrared absorption spectroscopy (SEIRAS) analysis. The results show that the Pt electrode has high oxidation activity and significant poison behavior; on the contrary, the Au electrode demonstrates low activity without a poison peak. The SEIRAS analyses reveal that both carbon monoxide (CO) and carbon dioxide (CO₂) appear during anode sweeping, and the CO peak density decreases with increasing potential and finally is eliminated. During the cathodic scanning, the CO peak reappears, and the peak intensity increases with scanning cycles, demonstrating a high poison behavior and the C1 reaction route on Pt. On the Au electrode, CO₂ and CO peaks were not observed; instead, an acetic acid peak appeared, indicating a C2 reaction path. For the Pt/Au composited electrodes, the electrochemical activities of the electrodes, as well as their poison behavior, increased with the deposition amount of Pt. However, the intensities of the poison peaks are smaller than those of oxidation ones; therefore, a higher tolerance to the CO poison can be achieved. For the 2 m-Pt/Au composite electrode, the activity is close to that of pure Pt, but the poison tolerance is 3 times the value of Pt.

Visible-Light-Driven Photocatalytic CO2 Reduction to CO/CH4 Using a Metal-Organic "Soft" Coordination Polymer Gel

The self-assembly of a well-defined and astutely designed, low-molecular weight gelator (LMWG) based linker with a suitable metal ion is a promising method for preparing photocatalytically active coordination polymer gels. Here, we report the design, synthesis, and gelation behaviour of a tetrapodal LMWG based on a porphyrin core connected to four terpyridine units (TPY-POR) through amide linkages. The self-assembly of TPY-POR LMWG with Ru^II ions results in a Ru-TPY-POR coordination polymer gel (CPG), with a nanoscroll morphology. Ru-TPY-POR CPG exhibits efficient CO₂ photoreduction to CO (3.5 mmol g^-1  h^-1 ) with >99 % selectivity in the presence of triethylamine (TEA) as a sacrificial electron donor. Interestingly, in the presence of 1-benzyl-1,4-dihydronicotinamide (BNAH) with TEA as the sacrificial electron donor, the 8e^- /8H⁺ photoreduction of CO₂ to CH₄ is realized with >95 % selectivity (6.7 mmol g^-1  h^-1 ). In CPG, porphyrin acts as a photosensitizer and covalently attached [Ru(TPY)₂ ]²⁺ acts as a catalytic center as demonstrated by femtosecond transient absorption (TA) spectroscopy. Further, combining information from the in situ DRIFT spectroscopy and DFT calculation, a possible reaction mechanism for CO₂ reduction to CO and CH₄ was outlined.

Pt-Mo/C, Pt-Fe/C and Pt-Mo-Sn/C Nanocatalysts Derived from Cluster Compounds for Proton Exchange Membrane Fuel Cells

Nanosized bimetallic PtMo, PtFe and trimetallic PtMoSn catalysts deposited on highly dispersed carbon black Vulcan XC-72 were synthesized from the cluster complex compounds PtCl(P(C6H5)3)(C3H2N2(CH3)2)Mo(C5H4CH3)(CO)3, Pt(P(C6H5)3)(C3N2H2(CH3)2)Fe(CO)3(COC6H5C2C6H5), and PtCl(P(C6H5)3)(C3N2H2(CH3)2)C5H4CH3Mo(CO)3SnCl2, respectively. Structural characteristics of these catalysts were studied using X-ray diffraction (XRD), microprobe energy dispersive spectroscopy (EDX), and transmission electron microscopy (TEM). The synthesized catalysts were tested in aqueous 0.5 M H2SO4 in a three-electrode electrochemical cells and in single fuel cells. Electrocatalytic activity of PtMo/C and PtFe/C in the oxygen reduction reaction (ORR) and the activity of PtMoSn/C in electrochemical oxidation of ethanol were evaluated. It was shown that specific characteristics of the synthesized catalysts are 1.5–2 times higher than those of a commercial Pt(20%)/C catalyst. The results of experiments indicate that PtFe/C, PtMo/C, and PtMoSn/C catalysts prepared from the corresponding complex precursors can be regarded as promising candidates for application in fuel cells due to their high specific activity.

Controllable Synthesis of Platinum-Tin Intermetallic Nanoparticles with High Electrocatalytic Performance for Ethanol Oxidation

This article proposes a general approach for the preparation of intermetallic nanoparticles of Pt3Sn, PtSn, PtSn2, and PtSn4, triggered by hexamethyldisilazane (HMDS) in conjunction with SnCl2. The ethanol oxidation reaction...

Synthesis of SDS-Modified Pt/Ti3C2Tx Nanocomposite Catalysts and Electrochemical Performance for Ethanol Oxidation

It is well-known that platinum (Pt) is still the preferred material of anode catalyst in ethanol oxidation, however, the prohibitive high cost and CO poisoning of Pt metal impede the commercialization of fuel cells. Therefore, improving the utilization rate of catalysts and reduce the cost of catalyst become one of the most concerned focus in the construction of fuel cells. In this work, the Pt-based catalysts are synthesized by using different content of sodium dodecyl sulfate (SDS) modified-Ti₃C₂T_x support, and the dispersion regulation function of SDS modified-Ti₃C₂T_x supported on Pt nanoparticles is investigated. The structure, composition and morphology of different catalysts are characterized by X-ray diffraction (XRD), X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and high-resolution TEM, respectively. It is found that the Pt nanoparticles in pure Ti₃C₂T_x surface are serious aggregated and show poor dispersion, whereas the Pt nanoparticles in SDS modified-Ti₃C₂T_x have a better dispersion. The electrochemical results revealed that SDS modified-Ti₃C₂T_x supported Pt nanoparticles has higher electrocatalytic activity and stability in both acidic and alkaline ethanol oxidation when the dosage of SDS increases to 100 mg. These findings indicate that the SDS-Ti₃C₂T_x/Pt catalysts show a promising future of potential applications in fuel cells with modification of Ti₃C₂T_x support.

Effect of Sn Doping on Pd Electro-Catalysts for Enhanced Electro-Catalytic Activity towards Methanol and Ethanol Electro-Oxidation in Direct Alcohol Fuel Cells

Carbon nano-onions (CNOs) were successfully synthesized by employing the flame pyrolysis (FP) method, using flaxseed oil as a carbon source. The alcohol reduction method was used to prepare Pd/CNOs and Pd-Sn/CNOs electro-catalysts, with ethylene glycol as the solvent and reduction agent. The metal-nanoparticles were supported on the CNO surface without adjusting the pH of the solution. High-resolution transmission electron microscopy (HRTEM) images reveal CNOs with concentric graphite ring morphology, and also PdSn nanoparticles supported on the CNOs. X-ray diffractometry (XRD) patterns confirm that CNOs are amorphous and show the characteristic diffraction peaks of Pd. There is a shifting of Pd diffraction peaks to lower angles upon the addition of Sn compared to Pd/CNOs. X-ray photoelectron spectroscopy (XPS) results also confirm the doping of Pd with Sn to form a PdSn alloy. Fourier transform infrared spectroscopy (FTIR) displays oxygen, hydroxyl, carboxyl, and carbonyl, which facilitates the dispersion of Pd and Sn nanoparticles. Raman spectrum displays two prominent peaks of carbonaceous materials which correspond to the D and G bands. The Pd-Sn/CNOs electro-catalyst demonstrates improved electro-oxidation of methanol and ethanol performance compared to Pd/CNOs and commercial Pd/C electro-catalysts under alkaline conditions.

Methanol, Ethanol, and Formic Acid Oxidation on New Platinum-Containing Catalysts

Electrooxidation of methanol, ethanol, and formic acid was studied on three platinum-containing electrocatalysts: PtCu/C, Pt/(SnO2/C), and Pt/C, Pt content being about 20 wt%. In all reactions, the integral specific activity of the catalysts, estimated from the results of cyclic voltammetry, grows in the Pt/C < Pt/(SnO2/C) < PtCu/C row. The influence of the reagent nature subjected to electrooxidation is manifested both in the difference of the absolute rate values of the corresponding reactions, decreasing in the order CH3OH > HCOOH > C2H5OH, and in the different ratio of these rates on different catalysts and at different potentials. Pt/(SnO2/C) catalyst containing SnO2 nanoparticles is the most active among the studied catalysts in methanol and formic acid electrooxidation reactions under potentiostatic conditions at the E = 0.60 V. Moreover, in formic acid electrooxidation reaction it is significantly superior to even the PtRu/C commercial catalyst. The reasons for the positive influence of Cu atoms and SnO2 nanoparticles on the catalytic activity of platinum are presumably associated with different effects: Interaction of the d-orbitals of copper and platinum atoms in bimetallic nanoparticles and implementation of the bifunctional catalysis mechanism on the adjacent platinum and tin dioxide nanoparticles.

The formation and antibacterial activity of Zn/ZnO nanoparticle produced in Pometia pinnata leaf extract solution using a laser ablation technique

The single-step green synthesis has been successfully established to prepare a bi-phase structure of Zn/ZnO nanoparticles using laser ablation in a liquid medium. Nd: YAG laser with the wavelength of 1064 nm was employed to perform the laser ablation in pure water and Pometia pinnata (P. pinnata) leaf extract, with the leaf, were extracted in pure water and some concentration of ethanol. ZnO nanoparticles can be obtained via laser ablation in pure water, while the usage of P. pinnata leaf extract as the solution has caused the appearance of the bi-phase Zn/ZnO nanostructure. X-ray diffraction (XRD) pattern indicates the appearance of Zn peaks alongside with ZnO peaks with the inclusion of P. pinnata leaf extract. Transmission electron microscope (TEM) images show the change of shape from the rod-like shape into a spherical shape and smaller size spherical shape of Zn/ZnO nanoparticles in comparison with ZnO. Noticeable change of UV-visible spectrum emerges as the water was substituted by P. pinnata leaf extract. The zeta potential of Zn/ZnO prepared with P. pinnata extracted in water, with the value of - 18.9 V, reduces down to - 43.5 and - 41.1 for 20-40% of ethanol concentration, respectively. The as-prepared ZnO and Zn/ZnO colloidal samples were evaluated for their antibacterial activities against two strains Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Zn/ZnO sample shows a more substantial antibacterial effect in comparison with pure ZnO, no bacteria alive after 12 and 24 h' treatment for E. coli and S. aureus, respectively.

Investigation of the thermal removal steps of capping agents in the synthesis of bimetallic iridium-based catalysts for the ethanol oxidation reaction

Two iridium-based catalysts (namely IrSn and IrNi) are synthesised via a polyol route involving capping agents.

Synthesis of free-standing ternary Rh-Pt-SnO2-carbon nanotube nanostructures as a highly active and robust catalyst for ethanol oxidation

The rational design of durable materials is an important issue for improving the performance of electrocatalysts towards the ethanol oxidation reaction (EOR). In this work, binderless thin nanostructured layers of SnO2, Pt, Rh, bilayers of Pt/SnO2, Rh/Pt and tri-layers of Rh (ca. 10 nm thickness)/PtSnO2 are directly grown by pulsed laser deposition onto carbon nanotubes (CNTs). SEM analysis shows that CNTs are perfectly coated with the catalysts. The onset potentials of the CO stripping and EOR indicate that Rh/Pt/SnO2 is the most active for the CO and the EOR. The incorporation of the CNTs in the catalyst layer is outstandingly beneficial to both the catalytic current activity and the durability. Indeed Rh/Pt/SnO2/CNT delivers mass activity as high as 213.42 mA mg-1 Pt. Moreover, Rh/Pt/SnO2/CNT demonstrates not only the lowest poisoning rate (by intermediate species, such as adsorbed CO) but also the highest durability current of 132.17 mA mg-1 Pt far superior to CNT-free Rh/Pt/SnO2/CP (58.33 mA mg-1 Pt). XPS shows that SnO2, Pt and Rh are all present at the surface of Rh/Pt/SnO2/CNT, the presence of two oxophilic materials like SnO2 and Rh, implies an earlier source of OHads-species, which facilitates the oxidation of CO and assuming a second contribution from Rh is to enhance the cleavage of the C-C bond for the complete oxidation of ethanol. The 3D porous and binderless structure, the low amount of the noble catalyst, the excellent electroactivity and durability of the Rh5/PtSnO2/CNT/CP composite represents an important step in advancing its use as an anode in commercial applications in DEFC.

Optimization of Pt-Oxygen-Containing Species Anodes for Ethanol Oxidation Reaction: High Performance of Pt-AuSnOx Electrocatalyst

Pt-oxygen-containing species (Pt-OCS) catalysts, in which OCS (e.g., metal-oxides) are decorated on a Pt surface, possess enhanced ethanol oxidation reaction (EOR) activity and stability compared with pure Pt and are promising in practical applications of direct ethanol fuel cells. We investigate the promotion roles of Pt-OCS electrocatalysts toward the EOR via a combination of density functional theory (DFT) calculations and experiments, providing a rational design strategy for Pt-OCS catalysts. It is revealed that Pt-AuO and Pt-SnO excel in EOR activity and stability, respectively, among the DFT screening of various Pt-OCS systems, and this is confirmed by the following experiments. Moreover, an optimized Pt-AuSnO catalyst is proposed by DFT calculations, taking advantage of both Pt-AuO and Pt-SnO. The as-prepared Pt-AuSnO catalyst delivers an EOR activity that is 9.7 times higher than that of Pt and shows desired stability. These findings are expected to elucidate the mechanistic insights into Pt-OCS materials and lead to advanced EOR electrocatalysts.

Applying potentials to conductive materials impairs High-loading anaerobic digestion performance by affecting direct interspecies electron transfer

In order to illustrate the impact that application of positive or negative potential to conductive materials can have on direct interspecies electron transfer (DIET) and reactor performance under high organic loading rates, three continuous laboratory-scale reactors with carbon-cloth electrodes poised at +0.7 V, -0.7 V (vs. Ag/AgCl) and no-potential were fed high concentrations of ethanol wastewater. While exoelectrogens and methanogens that are capable of DIET were significantly enriched in poised reactors, they performed worse than the non-current control. Volatile fatty acids (VFAs) accumulated more rapidly in the positively then negatively poised reactor, but neither could withstand high-loading rates. These results demonstrate that applying potential to conductive materials had a negative effect on anaerobic digestion under high-loading conditions.

Formation of microns long thin wire networks with a controlled spatial distribution of elements

By controlling the spatial distribution of elements using a simple self-assembly process, the catalytic performance can be enhanced.

Colloidal bimetallic platinum–ruthenium nanoparticles in ordered mesoporous carbon films as highly active electrocatalysts for the hydrogen evolution reaction

Ordered mesoporous carbon films with high surface area, good electrical conductivity and an improved distribution of NPs with tunable composition show high electrocatalytic activity in HER.

Ni(OH)2 Decorated Pt-Cu Octahedra for Ethanol Electrooxidation Reaction

Here we report the synthesis of 9 nm Ni(OH)2 decorated Pt-Cu octahedra (Ni(OH)2-PtCu) in one-pot synthesis for ethanol oxidation reaction (EOR) electrocatalysis in acidic electrolyte. To prepare Ni(OH)2-PtCu octahedra, CO gas was directly introduced in a reaction process as selective capping agents on the PtCu(111) facet. Ni(OH)2 was naturally deposited on the Pt-Cu octahedra during the synthesis. Carbon supported Ni(OH)2-PtCu (Ni(OH)2-PtCu/C) as an EOR catalyst showed enhanced CO tolerance due to the existence of oxophilic Ni(OH)2 on the surface of Pt-Cu, facilitating water dissolution to produce OH adsorption and to promote complete CO oxidation to CO2. In addition, Pt-Cu alloy composition also showed improvement of CO tolerance because of modified d-band structure of the Pt atoms, thereby weakening the binding strength of CO on the catalysts. Therefore, the Ni(OH)2-PtCu/C showed enhanced EOR activity and durability compared to the Pt-Cu octahedra and commercial Pt/C counterparts.

Conversion of bimetallic PtNi3 nanopolyhedra to ternary PtNiSn nanoframes by galvanic replacement reaction

Hollow multimetallic PtNiSn nanoparticles (NPs) were formed from solid Ni-core/Pt-frame NPs by the galvanic replacement reaction (GRR) of Ni by Sn. The GRR was performed by adding SnCl4·5H2O dissolved in ethylene glycol into the PtNi3 NPs containing suspension. The reaction yielded nanoframes with a hollow interior, having Pt-rich edges covered with a thin, incomplete Sn layer. They were investigated using transmission electron microscopy (TEM), energy dispersion X-ray spectroscopy (EDS) and X-ray diffraction (XRD). EDS analysis showed that the GRR rate could be modified by changing the solvent and the concentration of tin ions. Indeed, compared to water, ethylene glycol was found to facilitate the reduction of tin chloride and to affect nickel dissolution. TEM analysis revealed that the galvanic replacement of nickel and tin involves two different mechanisms. The first one consists of nickel oxidation followed by reduction of tin ions. In the second mechanism, oxidation of nickel and reduction of tin ions occur simultaneously.

NiSn nanoparticle-incorporated carbon nanofibers as efficient electrocatalysts for urea oxidation and working anodes in direct urea fuel cells

Synthesis of NiSn alloy nanoparticle-incorporated carbon nanofibers was performed by calcining electrospun mats composed of nickel acetate, tin chloride and poly(vinyl alcohol) under vacuum. The electrochemical measurements indicated that utilization of tin as a co-catalyst could strongly enhance the electrocatalytic activity if its content and calcination temperature were optimized. Typically, the nanofibers prepared from calcination of an electrospun solution containing 15 wt% SnCl2 at 700 °C have a current density almost 9-fold higher than that of pristine nickel-incorporated carbon nanofibers (77 and 9 mA/cm2, respectively) at 30 °C in a 1.0 M urea solution. Furthermore, the current density increases to 175 mA/cm2 at 55 °C for the urea oxidation reaction. Interestingly, the nanofibers prepared from a solution with 10 wt% of co-catalyst precursor show an onset potential of 175 mV (vs. Ag/AgCl) at 55 °C, making this proposed composite an adequate anode material for direct urea fuel cells. Optimization of the co-catalyst content to maximize the generated current density resulted in a Gaussian function peak at 15 wt%. However, studying the influence of the calcination temperature indicated that 850 °C was the optimum temperature because synthesizing the proposed nanofibers at 1000 °C led to a decrease in the graphite content, which dramatically decreased the catalyst activity. Overall, the study opens a new venue for the researchers to exploit tin as effective co-catalyst to enhance the electrocatalytic performance of the nickel-based nanostructures. Moreover, the proposed co-catalyst can be utilized with other functional electrocatalysts to improve their activity toward oxidation of different fuels.

Co-doped triel-pnicogen graphene as metal-free catalyst for CO oxidation: Role of multi-center covalency

Third and fifth group atoms, named triel and pnicogen, respectively, were used for graphene doping. AlP and AlN structures were selected as co-doped graphene-based catalysts. The electronic structure and catalytic properties of binary AlN, AlP co-doped graphene were investigated through density functional theory (DFT). Results show that the AlP co-doped graphene strictly enhances the oxygen reactivity compared to AlN one. The CO oxidation on AlP and AlN co-doped graphene sheets is mainly done through Eley-Rideal mechanism as follows: CO + O₂➔CO₂ + O_ads and CO + O_ads➔ CO₂. The CO oxidation reaction paths over the AlN and AlP-co-doped graphene have revealed that they can be regarded as the competent catalyst for CO oxidation in the presence of O₂. Mechanistically, both AlP and AlN co-doped graphene catalysts are appropriately active in the first step while the second step is too hard to do regarding the multi-center covalency character between O₂ and AlP co-doped graphene and hence its catalytic efficiency is significantly lower compared to AlN co-doped graphene sheet. Thus, the substitution of a C-C bond with Al-N is an effective way to design the graphene-based catalysts for CO oxidation.

Shaping well-defined noble-metal-based nanostructures for fabricating high-performance electrocatalysts: advances and perspectives

This review highlights recent advances in shaping protocols and structure-activity relationships of noble-metal-based catalysts with well-defined nanostructures in electrochemical reactions.

Quantitative in situ13C NMR studies of the electro-catalytic oxidation of ethanol

The newly developed pouch cells offer a sensitive method to analyse various products of electrocatalytic reactions, especially of the alcohol oxidation reaction.