Feasibility of ultra-low Pt loading electrodes for high temperature proton exchange membrane fuel cells based in phosphoric acid-doped membrane

Factors as the Pt/C ratio of the catalyst, the binder content of the electrode and the catalyst deposition method were studied within the scope of ultra-low Pt loading electrodes for high temperature proton exchange membrane fuel cells (HT-PEMFCs). The Pt/C ratio of the catalyst allowed to tune the thickness of the catalytic layer and so to minimize the detrimental effect of the phosphoric acid flooding. A membrane electrode assembly (MEA) with 0.05 mg_Ptcm⁻² at anode and 0.1 mg_Ptcm⁻² at cathode (0.150 mg_Ptcm⁻² in total) attained a peak power density of 346 mW cm⁻². It was proven that including a binder in the catalytic layer of ultra-low Pt loading electrodes lowers its performance. Electrospraying-based MEAs with ultra-low Pt loaded electrodes (0.1 mg_Ptcm⁻²) rendered the best (peak power density of 400 mW cm⁻²) compared to conventional methods (spraying or ultrasonic spraying) but with the penalty of a low catalyst deposition rate.     

Facile synthesis of cobalt modified 2D titanium carbide with enhanced hydrogen evolution performance in alkaline media

2D transition metal carbides, nitrides and carbonitrides, namely the MXenes, attract more and more attentions due to their unique properties. Here, we report a simple one-step molten salt etching method to prepare Co modified MXene hybrid (Ti₃C₂T_x:Co) by the reaction of Ti₃AlC₂ with Lewis acid CoCl₂ at 750 °C. Most of Co atoms aggregates in the interlayered space of Ti₃C₂T_x. Benefitting from the improved electron charge transfer efficiency and increased active sites, the sulfuric acid treated Ti₃C₂T_x:Co-12h hybrid exhibits excellent electrocatalytical activity for hydrogen evolution reaction in alkaline media, delivering a current density of 10 mA cm⁻² at an overpotential of 103.6 mV, which is lower than most noble metal free MXene based electrocatalysts. The results illustrate that the proposed method is very facile and useful to incorporate mid-to-late transition metals into the MXene phase to prepare MXene based HER electrocatalysts.     

Soybean powder enables the synthesis of Fe–N–C catalysts with high ORR activities in microbial fuel cell applications

The development of microbial fuel cells (MFCs) into a new type of carbon-neutral wastewater treatment technology requires efficient and low-cost oxygen reduction reaction catalysts in air cathodes. The use of raw soybean powder was investigated for synthesizing Fe–N–C ORR catalysts in a sacrificial SiO₂ support method. ZnCl₂ etching in the synthesis was found to facilitate the formation of hierarchical porous structures of Fe–N–C catalysts. Fe–N–C(1-1) catalyst synthesized with an optimal soybean/ZnCl₂ mass ratio of 1:1 exhibited the highest ORR activity in air cathodes. The use of the obtained Fe–N–C(1-1) catalyst enables a maximum power production of ~0.480 mW cm⁻² in MFCs, higher than commercial Pt/C (0.438 mW cm⁻²) with the same catalyst loading of 2 mg cm⁻². Long-term MFC operations demonstrated that the Fe–N–C synthesized from raw soybean have high stability and toxic tolerance, indicating that abundant low cost soybean biomass is a potential material for ORR catalyst development in MFC applications.     

Facile one-pot aqueous fabrication of interconnected ultrathin PtPbPd nanowires as advanced electrocatalysts for ethanol oxidation and oxygen reduction reactions

The catalytic features of Pt-based advanced materials closely correlate with the compositions, morphology and structure. Hence, interconnected trimetallic PtPbPd ultrathin nanowires (PtPbPd NWs) were synthesized by octylphenoxypolyethoxyethanol (NP-40)-mediated one-pot aqueous method, using in-situ generated hydrogen bubbles as the dynamic template. It is found that the types of the precursors and the amount of NP-40 are critical in this synthesis. The as-obtained architectures showed remarkable improvement in the electrocatalytic properties for ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR), surpassing those of commercial Pt/C (20 wt%), homemade PtPd NWs, PtPb NWs and PdPb NWs. Specifically, the mass activity (MA)/specific activity (SA) of PtPbPd NWs (1.20 A mg⁻¹/2.78 mA cm⁻²) is higher than those of Pt/C (0.86 A mg⁻¹/1.79 mA cm⁻²) in 0.5 M KOH solution. Furthermore, the as-synthesized catalyst displayed a positive-shift of the onset potential (E_onset, 0.993 V) for ORR over Pt/C (0.895 V) in 0.1 M KOH electrolyte. These scenarios manifest that this approach provides some new valuable guidelines for preparing novel trimetallic nanocatalysts in energy storage and conversion applications.     

Investigation of the effect of graphitized carbon nanotube catalyst support for high temperature PEM fuel cells

In this study, it is aimed to investigate the graphitization effect on the performance of the multi walled carbon nanotube catalyst support for high temperature proton exchange membrane fuel cell (HT-PEMFC) application. Microwave synthesis method was selected to load Pt nanoparticles on both CNT materials. Prepared catalyst was analyzed thermal analysis (TGA), Transmission Electron Microscopy (TEM) and corrosion tests. TEM analysis proved that a distribution of Pt nanoparticles with a size range of 2.8–3.1 nm was loaded on the Pt/CNT and Pt/GCNT catalysts. Gas diffusion electrodes (GDE) were manufactured by an ultrasonic spray method with synthesized catalyst. Polybenzimidazole (PBI) membrane based Membrane Electrode Assembly (MEA) was prepared for observe the performance of the prepared catalysts. The synthesized catalysts were also tested in a HT-PEMFC environment with a 5 cm² active area at 160 °C without humidification. This study demonstrates the feasibility of using the microwave synthesis method as a fast and effective method for preparing high performance Pt/CNT and Pt/GCNT catalyst for HT-PEMFC. The HT-PEMFC performance evaluation shows current densities of 0.36 A/cm²0.30 A/cm² and 0.20 A/cm² for the MEAs prepared with Pt/GCNT, Pt/CNT and Pt/C catalysts @ 0.6 V operating voltage, respectively. AST (Accelerated Stress Test) analyzes of MEAs prepared with Pt/GCNT and Pt/CNT catalysts were also performed and compared with Pt/C catalyst. According to current density @ 0.6 V after 10,000 potential cycles, Pt/GCNT, Pt/CNT and Pt/C catalysts can retain 61%, 67% and 60% of their performance, respectively.     

Polybenzimidazole-modified carbon nanotubes as a support material for platinum-based high-temperature proton exchange membrane fuel cell electrocatalysts

We fabricate polybenzimidazole (PBI) wrapped carbon nanotubes (MWCNTs) as support material for platinum-based fuel cell electrocatalyst. With the aid of microwave-assisted polyol reduction, we obtain very fine platinum (Pt) nanoparticles on PBI/MWCNT support while reducing the amount of Pt waste during synthesis. Cyclic voltammetry (CV) concludes that Pt-PBI/MWCNT has 43.0 m² g⁻¹ of electrochemically active surface area (ECSA) to catalyze hydrogen oxidation. Furthermore, after the 1000th cycle, Pt-PBI/MWCNT preserves almost 80% of its maximum ECSA, meaning that Pt-PBI/MWCNT is much more durable than the Pt/MWCNT and commercial Pt/C. High-temperature proton exchange membrane fuel cell (HT-PEMFC) performance tests are conducted under H₂/Air conditions at the temperatures ranging from 150 °C to 180 °C. Nevertheless, tests conclude that the maximum power density values of the Pt-PBI/MWCNT are found inferior to the Pt/C at all temperatures (e.g., 47 vs. 62 mW cm⁻² at 180 °C), suggesting that some balance between durability and performance has to be taken into consideration.     

Lattice-strained Pt nanoparticles anchored on petroleum vacuum residue derived N-doped porous carbon as highly active and durable cathode catalysts for PEMFCs

High cost and poor durability of Pt-based cathode catalysts for oxygen reduction reaction (ORR) severely hamper the popularization of proton exchange membrane fuel cells (PEMFCs). Tailoring carbon support is one of effective strategies for improving the performance of Pt-based catalysts. Herein, petroleum vacuum residue was used as carbon source, and nitrogen-doped porous carbon (N-PPC) was synthesized using a simple template-assisted and secondary calcination method. Small Pt nanoparticles (Pt NPs) with an average particles size of 1.8 nm were in-situ prepared and spread evenly on the N-PPC. Interestingly, the lattice compression (1.08%) of Pt NPs on the N-PPC (Pt/N-PPC) was clearly observed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), which was also verified by the shift of (111) crystal plane of Pt on N-PPC to higher angles. The X-ray photoelectron spectroscopy (XPS) results suggest that the N-PPC support had a strong effect on anchoring Pt NPs and endowing surface Pt NPs with lowered d band center. Thus, the Pt/N-PPC as a catalyst simultaneously boosted the ORR activity and durability. The specific activity (SA) and mass activity (MA) of the Pt/N-PPC at 0.9 V reached 0.83 mA cm⁻² and 0.37 A mg_Pt⁻¹, respectively, much higher than those of the commercial Pt/C (0.21 mA cm⁻² and 0.11 A mg_Pt⁻¹) in 0.1 M HClO₄. The half-wave potential (E_1/2) of Pt/N-PPC exhibited only a minimal negative shift of 7 mV after 30,000 accelerated durability tests (ADT) cycles. More importantly, an H₂–O₂ fuel cell with a Pt/N-PPC cathode achieved a power density of 866 mW cm⁻², demonstrating that the prepared catalyst has a promising application potential in working environment of PEMFCs.     

Quasi zero-dimensional MoS2 quantum dots decorated 2D Ti3C2Tx MXene as advanced electrocatalysts for hydrogen evolution reaction

Developing advanced noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) is still a great challenge. Herein, a novel HER catalyst with quasi zero-dimensional (0D) MoS₂ quantum dots (QDs) supported on two-dimensional (2D) Ti₃C₂T_x MXene nanosheets is facilely synthesized. The MoS₂ QDs/Ti₃C₂T_x nanohybrid retains the unique layer structure, and the MoS₂ QDs are in situ formed and distributed uniformly. The obtained MoS₂ QDs/Ti₃C₂T_x catalyst exhibits superior electrocatalytic activity due to its excellent conductivity, abundant of active sites exposed and a high percentage of 1T metallic phase (～76%) of MoS₂ QDs. Remarkably, an early HER overpotential of 220 mV at 10 mA cm^?2 and a small Tafel slope of 72 mV dec^?1 of MoS₂ QDs/Ti₃C₂T_x are achieved in 0.5 M H₂SO₄ solution. In addition, the exchange current density of MoS₂ QDs/Ti₃C₂T_x is ～5 times larger compared with pure MoS₂, thus demonstrating an accelerated charge transfer during the electrocatalytic process.     

Precise control of π-conjugated polymer/carbon nanotubes heterointerfaces for oxygen reduction reactions

Nitrogen-coordinated metal catalyst has been regarded as a promising candidate for precious platinum for oxygen reduction reaction (ORR). However, controlling the structure and composition of coordinated metals in heterogeneous catalysts remains a synthetic bottleneck. Here, we design and fabricate π-conjugated polymer/CNTs heterointerfaces by polymerizing Co-BTA on CNTs. Co-BTA contains abundant Co–N₄ moieties and provides catalytic sites for ORR. CNT acts as a support and constructs the network for electron transport. Therefore, Co-BTA/CNT exhibits outstanding catalytic activity for ORR with comparable half-wave potential to commercial Pt/C. Furthermore, Co-BTA/CNT demonstrates better durability and methanol tolerance compared with Pt/C. Importantly, zinc-air batteries with Co-BTA/CNT have a maximum discharge power of 94.5 mW cm⁻² and a high energy density of 985 Wh kg⁻¹, superior to that with commercial Pt/C (51.5  mW cm⁻², 930 Wh kg⁻¹). This work paves a new avenue for precisely controlling nitrogen-coordinated metal catalysts for electrochemical energy conversion and storage.     

Construction of Co-decorated 3D nitrogen doped-carbon nanotube/Ti3C2Tx-MXene as efficient hydrogen evolution electrocatalyst

Rational design of transition metal catalysts with robust and durable electrocatalytic activity for hydrogen evolution reactions (HER) is extremely important for renewable energy conversion and storage, as well as water splitting. Heteroatom doping has emerged as a feasible strategy for enhancing electrocatalytic activity. Here, cobalt nanoparticles (Co-NPs) were coated with nitrogen-doped carbon nanotubes (NCNTs) prepared via an in situ growth on accordion-like Ti₃C₂T_x-MXene (Co-NCNT/Ti₃C₂T_x). Such an intriguing structure showed great features: abundant anchoring sites for NCNT in situ growth, intimate integration of Co-NPs and NCNTs, high-speed electron transfer between 1D NCNTs and 2D Ti₃C₂T_x-MXenes, and a large number of effective catalytic active sites. This Co-NCNT/Ti₃C₂T_x hybrid catalyst was demonstrated to possess excellent HER performance with low overpotential (η₁₀, 190 mV), small Tafel slope (78.4 mV dec⁻¹), large electrochemically active surface area, and good long-term stability, thus outperforming many reported electrocatalysts. The present strategy provided a facile route for the design of transition metal HER catalysts with NCNT and MXene.     

High conductivity of novel Ti0.9Ir0.1O2 support for Pt as a promising catalyst for low-temperature fuel cell applications

The novel nanostructured Ti_0.9Ir_0.1O₂ acting as a potential catalyst support for Pt in fuel cell applications was easily synthesized by means of a facile and simple low-temperature hydrothermal process without using any surfactants and further heat treatment. Interestingly, even in low iridium doping concentration, the Ti_0.9Ir_0.1O₂ support possessed the high electronic conductivity of 0.016 S/cm, which was ∼10⁵ times as high as pure TiO₂ (4.15 × 10⁻⁷ S/cm), suggesting the efficient doping of iridium into TiO₂ lattice. Furthermore, the modified chemical reduction route utilized to prepare the 20 wt % Pt/Ti_0.9Ir_0.1O₂ electrocatalyst exhibited the good anchoring and uniform distribution of Pt nanoparticles (NPs) (∼3 nm) over Ti_0.9Ir_0.1O₂ surface and thus eventually resulted in the high electrochemical surface area (∼85.08 m²/gPt) compared to that of the commercial 20 wt % Pt/C (E-TEK) catalyst (∼69.21 m²/gPt). The cyclic voltammetry results in the methanol media revealed that the 20 wt % Pt/Ti_0.9Ir_0.1O₂ displayed the superior electrocatalytic activity compared to the 20 wt % Pt/C (E-TEK) catalyst towards the methanol electro-oxidation. For instance, the 20 wt % Pt/Ti_0.9Ir_0.1O₂ catalyst possessed the higher oxidation current density (∼28.8 mA/cm²), the lower onset potential (∼0.12 V) and the higher I_f/I_b ratio in comparison with the commercial 20 wt % Pt/C (E-TEK) catalysts. It is worth noting that the chronoamperometry results also indicated that the 20 wt % Pt/Ti_0.9Ir_0.1O₂ exhibited higher durability than the commercial 20 wt % Pt/C (E-TEK) catalyst. Beside introducing novel Ti_0.9Ir_0.1O₂ material, these results also offer a pathway of exploring the low dopants content of Ti_xIr_1-xO₂ material to serve as a good catalyst support for many fuel cell applications.     

Reformate gas composition and pressure effect on CO tolerant Pt/Ti0.8Mo0.2O2–C electrocatalyst for PEM fuel cells

Mixed-oxide coated Ti_0.8Mo_0.2O₂–C composite supported 20 wt% Pt electrocatalysts with Ti_0.8Mo_0.2O₂/C=75/25 mass ratio were developed for CO tolerance of polymer electrolyte membrane fuel cell (PEMFC) anode. Studies of the structure, composition and stability, as well as the results of CO_ads stripping confirmed that the mixed oxide composite support and the electrocatalyst prepared for this study show the well-documented characteristics of the Pt/Ti_1-xMo_xO₂-C systems with enhanced CO tolerance compared to the Pt/C catalyst.Dilution of hydrogen with CO₂ and CH₄ had negligible negative impact on the fuel cell performance. Switching gas composition between hydrogen and reformate shows recovery of potential after CO poisoning. Nevertheless, anode catalyst loading of 0.25 and 0.5 mgPt/cm² was not enough to give reasonable performance when CO impurity was present. Loading of 0.85 mgPt/cm² Ti_0.8Mo_0.2O₂–C supported catalyst was effective to give 1000 mA/cm² current density at 0.6 V under 25 ppm CO and 30 psig. Higher loading was needed at mass transfer limited region to overcome poisoning. However, loadings higher than 0.85 mgPt/cm² caused mass transfer limitations. Hence higher loadings is proposed with 40 wt% Pt/Ti_0.8Mo_0.2O₂–C support catalyst.     

Multi-walled carbon nanotubes decorated by platinum catalyst for high temperature PEM fuel cell

In the literature, studies on platinum catalysts deposited on multi-walled carbon nanotube (Pt/MWCNT) have been mostly focused on low temperature fuel cell (LT-PEMFC) applications. In this study, we focus the synthesis and characterization of high temperature fuel cell (HT-PEMFC) performance of Pt/MWCNT in short and long term. The structural properties of the Pt/MWCNT electrocatalyst were analyzed by XRD, TGA, SEM and TEM measurements. The Pt/MWCNTs were also characterized by electrochemical measurements for durability estimation. Laboratory scale MEA with Pt/MWCNT was prepared by ultrasonic coating technique and has been tested in situ in single HT-PEMFC. Performance curves in dry Hydrogen/Air system were obtained that demonstrated performance comparable to commercial catalysts in that HT-PEMFC. The characterizations specified that the electrocatalytic and HT-PEMFC performance of the Pt/MWCNT catalysts are higher power density (0.360 W/cm²) than Pt/C (0.310 W/cm²) at 160 °C. The results obtained show that the synthesized catalysts are suitable for high temperature applications. In addition, the stability studies of MEAs prepared with Pt/MWCNT catalyst were performed by AST tests and compared with Pt/C based MEA.     

Boosting the dehydrogenation efficiency of dodecahydro-N-ethylcarbazole by assembling Pt nanoparticles on the single-layer Ti3C2Tx MXene

As the candidates for large-scale hydrogen storage, liquid organic hydrogen carriers (LOHCs) exhibit evident advantages in hydrogen storage density and convenience of storage and transportation. Among them, NECZ (N-ethylcarbazole)/12H-NECZ (dodecahydro-N-ethylcarbazole) is considered as a typical system with the lower hydrogenation/dehydrogenation temperature. However, the low dehydrogenation efficiency restrict its commercial applications. In this work, the single-layer Ti₃C₂T_x MXene was employed as the support to load the Pt nanoparticles for the 12H-NECZ dehydrogenation reaction. The effect of transition metals, loading amounts and morphologies of catalysts were analyzed. It was found that the 3 wt% Pt/S–Ti₃C₂T_x catalyst exhibited the best catalytic performance with 100% conversion, 91.55% selectivity of NECZ and 5.62 wt% hydrogen release amount at 453 K, 101.325 kPa for 7 h. The product distributions and kinetics analysis suggested that the elementary reaction from 4H-NECZ to NECZ was the rate-limiting step. The selectivity of NECZ is sensitive to the dehydrogenation temperature. Combined with the XRD, SEM, HRTEM, XPS, BET and FT-IR results, it could be indicated that the special two-dimension structure of S–Ti₃C₂T_x and electronic effect between Pt and S–Ti₃C₂T_x enhanced the dehydrogenation efficiency of 12H-NECZ. The measurements of cyclic dehydrogenation indicated that the Pt/S–Ti₃C₂T_x catalyst exhibited good stability after 42 h. This work brought a new strategy for the design of efficient catalysts using two-dimensional materials in the applications of the liquid organic storage hydrogen technology.     

Graphene based catalyst supports for high temperature PEM fuel cell application

In this study, the effect of graphene nanoplatelet (GNP) and graphene oxide (GO) based carbon supports on polybenzimidazole (PBI) based high temperature proton exchange membrane fuel cells (HT-PEMFCs) performances were investigated. Pt/GNP and Pt/GO catalysts were synthesized by microwave assisted chemical reduction support. X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Brauner, Emmet and Teller (BET) analysis and high resolution transmission electron microscopy (HRTEM) were used to investigate the microstructure and morphology of the as-prepared catalysts. The electrochemical surface area (ESA) was studied by cyclic voltammetry (CV). The results showed deposition of smaller Pt nanoparticles with uniform distribution and higher ECSA for Pt/GNP compared to Pt/GO. The Pt/GNP and Pt/GO catalysts were tested in 25 cm² active area single HT-PEMFC with H₂/air at 160 °C without humidification. Performance evaluation in HT-PEMFC shows current densities of 0.28, 0.17 and 0.22 A/cm² for the Pt/GNP, Pt/C and Pt/GO catalysts based MEAs at 160 °C, respectively. The maximum power density was obtained for MEA prepared by Pt/GNP catalyst with H₂/Air dry reactant gases as 0.34, 0.40 and 0.46 W/cm² at 160 °C, 175 °C and 190 °C, respectively. Graphene based catalyst supports exhibits an enhanced HT-PEMFC performance in both low and high current density regions. The results indicate the graphene catalyst support could be utilized as the catalyst support for HT-PEMFC application.     

Boron doping induced electronic reconfiguration of Fe-Nx sites in N-doped carbon matrix for efficient oxygen reduction reaction in both alkaline and acidic media

Developing non-precious metal-based catalysts as the substitution of precious catalysts (Pt/C) in oxygen reduction reaction (ORR) is crucial for energy devices. Herein, a template and organic solvent-free method was adopted to synthesize Fe, B, and N doped nanoflake-like carbon materials (Fe/B/N–C) by pyrolysis of monoclinic ZIF-8 coated with iron precursors and boric acid. Benefiting from introducing B into Fe–N–C, the regulated electron cloud density of Fe-N_x sites enhance the charge transfer and promotes the ORR process. The as-synthesized Fe/B/N–C electrocatalyst shows excellent ORR activity of a half-wave potential (0.90 V vs 0.87 V of Pt/C), together with superior long-term stability (95.5% current density retention after 27 h) in alkaline media and is even comparable to the commercial Pt/C catalyst (with a half-wave potential of 0.74 V vs 0.82 V of Pt/C) in an acidic electrolyte. A Zn-air battery assembled with Fe/B/N–C as ORR catalyst delivers a higher open-circuit potential (1.47 V), specific capacity (759.9 mA h g^?1_Zn at 10 mA cm^?2), peak power density (62 mW cm^?2), as well as excellent durability (5 mA cm^?2 for more than 160 h) compared to those with commercial Pt/C. This work provides an effective strategy to construct B doped Fe–N–C materials as nonprecious ORR catalyst. Theoretical calculations indicate that introduction of B could induce Fe-N_x species electronic configuration and is favorable for activation of OH1 intermediates to promote ORR process.     

Ultrafine Ru nanoparticles derived from few-layered Ti3C2Tx MXene templated MOF for highly efficient alkaline hydrogen evolution

It is meaningful to search high-efficient and inexpensive electrocatalysts for hydrogen evolution reaction (HER) due to the energy crisis and environmental pollution. Here, we report the preparation of ultrafine Ru nanoparticles from a hybrid of ZIF-L(Co) MOF and polydopamine coated few-layered Ti₃C₂T_x MXene (FL-Ti₃C₂T_x). FL-Ti₃C₂T_x is used as a template to grow regular leaf-shaped ZIF-L(Co) nanosheets through the reaction of Co ions anchored on the MXene surface with 2-methylimidazole. The obtained hybrid is then doped with Ru ions through ion exchange between Ru and Co ions, followed by thermal annealing at a temperature of 350 °C in an Ar atmosphere to produce ultrafine Ru nanoparticles. The obtained Ru@ZIF-L(Co)/FL-Ti₃C₂T_x nanocomposite shows outstanding HER performance with a low overpotential of 16.2 mV at a current density of 10 mA cm^?2, a small Tafel slope of 21.0 mV dec^?1 and excellent stability in 1.0 M KOH solution. This work provides a new strategy for the design and synthesis of highly efficient HER catalyst via MOFs with tunable composition and structure.     

Enhanced activity of Pt nanoparticle catalysts supported on manganese oxide-carbon nanotubes for ethanol oxidation

Pt nanoparticles deposited on manganese oxide-carbon nanotubes (Pt/MnO_x-CNTs) are prepared by a microwave-assisted polyol method. Their structure characterizations are carried out by Fourier transform infrared spectrometry (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) measurements, indicating that MnO_x nanoparticles cover the surface of CNTs and then Pt nanoparticles are uniformly dispersed on MnO_x-CNTs with the average particle size of about 2.2 nm. Ethanol oxidation peak current on Pt/MnO_x-CNTs (1141.4 mA mg⁻¹ Pt) is 1.82 times higher than that on Pt/CNTs (626.4 mA mg⁻¹ Pt) and 1.28 times higher than that on PtRu/C (JM) (888.6 mA mg⁻¹ Pt). The Pt/MnO_x-CNT catalyst presents not only excellent electrocatalytic activity and very high stability for ethanol oxidation, but also high tolerance to the poisonous carbonaceous intermediates generated during ethanol oxidation compared to Pt/CNT catalyst. This is attributed to the excellent proton conductivity of MnO_x and the synergistic effect between Pt and MnO_x. The optimum mass ratio of MnO_x to CNTs is 1:1 in the Pt/MnO_x-CNT catalysts.     

Kinetics and electrocatalytic activity of IrCo/C catalysts for oxygen reduction reaction in PEMFC

The purpose of this study is to develop a novel binary Iridium-Cobalt/C catalyst as a suitable substitute for platinum/C applied in proton exchange membrane fuel cells (PEMFCs). The carbon-supported IrCo catalysts were successfully synthesized using IrCl₃ and C₄H₆CoO₄ as the Ir and Co precursors respectively, in ethylene glycol (EG) refluxing at 120 °C. The nanostructured catalysts were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscope (TEM). Homogeneous catalyst particles supported on carbon showed a size of proximately 2 nm. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were conducted for the characterization of the catalyst performances. With a cathodic loading of 0.4 mg_Ir cm⁻², 20%Ir-30%Co/C achieved a maximum power density of 501.6 mW cm⁻² at 0.418 V, with a 50 cm² H₂/O₂ single cell. Although such a performance is about 26% lower than commercial Pt/C catalyst, it is still helpful in terms of Pt replacement and cost reduction.     

Silicon monoxide assisted synthesis of Ru modified carbon nanocomposites as high mass activity electrocatalysts for hydrogen evolution

Extremely low content of Ruthenium (Ru) nanoparticles were loaded on the carbon black (Ru/C) via reducing Ru ions with silicon monoxide. The obtained Ru/C nanocomposites exhibit an exciting electrochemical catalytic activity for hydrogen evolution reaction (HER) in the oxygen-free 0.5 M H₂SO₄ medium. The optical one (Ru/C-2) with a low Ru amount of 2.34% shows higher activity than previously reported Ru-based catalysts. The overpotential at 10 mA cm⁻² is 114 mV and the Tafel slope is 67 mV·dec⁻¹. Ru/C-2 catalyst also has good stability. The overpotential that afford the current density of 10 mA cm⁻² of 20 wt% Pt/C increased 92 mV while that of Ru/C-2 only increased 50 mV after a 30,000 s chronopotentiometry test. Furthermore, the mass activity of Ru/C-2 catalyst is even better than that of the commercial 20 wt% Pt/C when the overpotential is larger than 0.18 V. This silicon monoxide-mediated strategy may open a new way for the fabrication of high performance electrocatalysts.