Synthesis and characterization the multifunctional nanostructures TixW1-xO2 (x = 0.5; 0.6; 0.7; 0.8) supports as robust non-carbon support for Pt nanoparticles for direct ethanol fuel cells

In the present study, various mesoporous Ti_xW_1-xO₂ (x = 0.5; 0.6; 0.7; 0.8) supports were fabricated via a facile solvothermal approach and explored the effect of doping tungsten concentration on electrochemical properties of Ti_xW_1-xO₂-supported Pt electrocatalysts toward ethanol electrochemical reaction. Interestingly, the incorporation of tungsten into TiO₂ lattices with the doping tungsten amounts (20 and 30 at %) resulted in boosting both the surface area and electrical conductivity, however, a reverse trend was observed when increasing the doped tungsten content more than 40 at %. Additionally, the relatively well-distributed Pt nanoparticles with the small particle size (ca. 3 nm) anchored on supports were achieved using a microwave-assisted polyol route. Electrochemical results indicated that various Ti_xW_1-xO₂-supported Pt catalysts exhibited the catalytic performance greater than that of the commercial carbon-supported Pt (E-TEK) catalyst for ethanol electro-oxidation reaction (EOR). For as-obtained electrocatalysts, the Ti_0.7W_0.3O₂-supported Pt catalyst showed the highest mass activity (~260.23 mA/mg_Pt) and greatest I_f/I_b ratio (~1.34), which ~2.0-fold and ~1.57-time higher than that of carbon-supported Pt (E-TEK) catalyst (~130.62 mA/mg_Pt for mass activity and ~0.85 for I_f/I_b ratio, respectively). After 5000 cycling tests, the mass activity loss of Ti_xW_1-xO₂-supported Pt catalysts was around twice lower than that of the commercial Pt/C (E-TEK) catalysts, suggesting that the Ti_xW_1-xO₂-supported Pt catalysts exhibited the superior stability toward ethanol electrochemical oxidation. The outstanding electrochemical activity and stability of Ti_xW_1-xO₂-supported Pt electrocatalysts were owing to the synergetic effect between Pt nanocatalyst and non-carbon Ti_xW_1-xO₂ supports as well as superior natural durability of TiO₂-based materials.     

High conductivity and surface area of Ti0.7W0.3O2 mesoporous nanostructures support for Pt toward enhanced methanol oxidation in DMFCs

For the first time, a novel Pt catalyst supported on mesoporous Ti_0.7W_0.3O₂ nanoparticles, which exhibited superior advantages such as high conductivity (0.022 S/cm), large specific surface area (201.481 m²/g) and homogeneous morphology with 9 nm spherical-like particles, was prepared successfully via the rapid microwave-assisted polyol route. It is found that uniform 3 nm spherical-like Pt nano-forms were adhered homogeneous on the surface of Ti_0.7W_0.3O₂. Intriguingly, the electrochemical surface area of Pt catalyst supported on mesoporous Ti_0.7W_0.3O₂ was found to be around 90.05 m²/gPt, which is profoundly higher than ECSA value obtained from Pt/C (E-TEK) catalyst. Furthermore, as for methanol oxidation reaction measurement, the I_f/I_b ratio of the 20 wt % Pt/Ti_0.7W_0.3O₂ catalyst was found to be approximately 2.33, which 2.5-folds higher than that of the commercial Pt/C (E-TEK) catalyst. Importantly, the chronoamperometry data also revealed that the 20 wt % Pt/Ti_0.7W_0.3O₂ catalyst possessed the higher durability than the commercial 20 wt % Pt/C (E-TEK) catalyst. In addition, the successful synthesis of the 20 wt % Pt/Ti_0.7W_0.3O₂ catalyst not only offers an attractive catalyst for fuel cell using methanol but also opens application potentials for solar cells, as well as biosensors.     

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.     

Ti3C2Tx nanosheets with uniformly anchored Ru nanoparticles for efficient acidic and basic hydrogen evolution reaction

Developing an efficient and stable electrocatalyst for hydrogen evolution reaction (HER) remains critically signi?cance for renewable hydrogen production. Herein, a facile electrochemical reduction method was proposed to fabricate Ru nanoparticles (NPs) evenly anchored on Ti₃C₂T_x nanosheets (Ti₃C₂T_x-NS) electrocatalyst (Ru@Ti₃C₂T_x-NS). Interestingly, owing to the interaction between Ru NPs and Ti₃C₂T_x-NS, the resultant Ru@Ti₃C₂T_x-NS electrocatalyst performed a Pt-like electrocatalytic property for HER under the acidic solution with an ultra-low overpotential of 46.75 mV to reach ?10 mA/cm², a small Tafel slope of 30.6 mV/dec, and long-term stability. Simultaneously, the Ru@Ti₃C₂T_x-NS also displayed splendid HER electrocatalytic performance in the basic condition. Furthermore, Ru@Ti₃C₂T_x-NS showed a lower value of Gibbs free energy for HER (?0.21 eV) than either pure Ru or Ti₃C₂T_x-NS from the theoretical calculation results. It is expected that such a promising approach would be extended to design and fabricate other noble metal NPs anchored MXene nanosheets for HER application.     

Platinum: A key element in electrode composition for reversible chloralkaline electrochemical cells

In this work, the performance of a reversible electrochemical cell using three different electrodes (Ti/Ru_0.5Ir_0.5O₂, Ti/Ru_0.3Ti_0.7O₂, and Ti/Ru_0.3Ti_0.6O₂Pt_0.1) is evaluated and compared for the oxidation of chlorides and reduction of chlorine. Results indicate that this technology is successful and that its efficiency depends significantly on the composition of the electrode in charge of the chlorine electrochemistry. Operating at 0.5 V allows us to obtain near 7 mA cm⁻² and power efficiencies around 120 Wh mmol⁻¹ hydrogen supplied. In electrolytic mode, efficiencies around 4 mol Cl₂ mWh⁻¹ can be obtained. The best performance is shown by the Ti/Ru_0.3Ti_0.6O₂Pt_0.1 electrode resulting from its roughest morphology and the presence of Pt. In shifting from electrolyzer to fuel cell mode, the current produced is rapidly stabilized for Ti/Ru_0.3Ti_0.6O₂Pt_0.1 and Ti/Ru_0.5Ir_0.5O₂ electrodes. However, the electrode Ti/Ru_0.5Ir_0.5O₂ showed a progressive change, which suggests a change in its composition that negatively affects the system.     

Study of ethanol electro-oxidation in acid environment on Pt3Sn/C anode catalysts prepared by a modified polymeric precursor method under controlled synthesis conditions

A carbon-supported binary Pt₃Sn catalyst has been prepared using a modified polymeric precursor method under controlled synthesis conditions. This material was characterized using X-ray diffraction (XRD), and the results indicate that 23% (of a possible 25%) of Sn is alloyed with Pt, forming a dominant Pt₃Sn phase. Transmission electron microscopy (TEM) shows good dispersion of the electrocatalyst and small particle sizes (3.6 nm ± 1 nm). The polarization curves for a direct ethanol fuel cell using Pt₃Sn/C as the anode demonstrated improved performance compared to that of a PtSn/C E-TEK, especially in the intrinsic resistance-controlled and mass transfer regions. This behavior is probably associated with the Pt₃Sn phase. The maximum power density for the Pt₃Sn/C electrocatalyst (58 mW cm⁻²) is nearly twice that of a PtSn/C E-TEK electrocatalyst (33 mW cm⁻²). This behavior is attributed to the presence of a mixed Pt₉Sn and Pt₃Sn alloy phase in the commercial catalysts.     

Alumina supported nano-platinum on copper nanoparticles prepared via galvanic displacement reaction for preferential carbon monoxide oxidation in presence of hydrogen

Improved catalytic centres with a minimum mass-loading of expensive platinum (Pt) have been anticipated for various catalytic applications, for instance preferential oxidation (PROX) of carbon monoxide (CO) in the presence of Hydrogen. Here, we report the synthesis of nano-Pt on the surface of copper (Cu) nanoparticles (NPs) supported on γ-Al₂O₃ (Pt_n(Cu)/γ-Al₂O₃) via galvanic displacement reaction (GDR) for the catalytic CO-PROX reaction. Pt_n(Cu)/γ-Al₂O₃ showed much improved CO-PROX performance compared to that of the as-synthesized Pt_l(Cu)/γ-Al₂O₃ catalyst. Importantly, no significant conversion of hydrogen at a lower temperature range (<200 °C) is observed during the CO-PROX reaction which is one of the essential prerequisites for the CO-PROX reaction. Moreover, Pt_n(Cu)/γ-Al₂O₃ showed the durable, long-term catalytic CO-PROX performance for 120 h. These results infer that realization of nano-Pt on the surface of the Cu NPs holds the promise as the catalytic centres with the minimum mass-loading of Pt for the CO-PROX reaction.     

Electrochemical behaviour of carbon supported Pt electrocatalysts for H2O2 reduction

Carbon supported bimetallic Pt-alloys (Pt_0.75M_0.25/C, with M = Ni or Co) are investigated as novel electrode materials for H₂O₂ reduction in acid solution. The alloy electrocatalysts, Pt_0.75Ni_0.25/C and Pt_0.75Co_0.25/C, as well as carbon supported Pt (Pt/C) are characterised using cyclic voltammetry. The electrocatalytic activity of the materials is studied using a rotating disc electrode system with a combination of linear scan voltammetry and chronoamperometry. It is found that the activity of Pt_0.75M_0.25/C electrocatalysts for H₂O₂ reduction is comparable to the activity of Pt/C electrocatalyst, with Pt_0.75Co_0.25/C exhibiting the best performance.     

Highly efficient and ORR active platinum-scandium alloy-partially exfoliated carbon nanotubes electrocatalyst for Proton Exchange Membrane Fuel Cell

Oxygen reduction reaction (ORR) in Proton Exchange Membrane Fuel Cell (PEMFC) is the most sluggish reaction, which impedes the performance and commercialization of PEMFC. Platinum-based alloys show higher ORR activity than Pt and it is suggested by density functional theory calculations that Pt₃Sc alloy has high stability and higher ORR activity due to filling the metal d-bands and lowers binding energy of the oxygen species respectively. Herein, we report Pt₃Sc alloy nanoparticles (NPs) dispersed over partially exfoliated carbon nanotubes (PECNTs) as a cathode catalyst for single-cell measurements of PEMFC where Pt₃Sc alloy shows a lower binding energy towards oxygen and facilitates ORR with much faster kinetics. The ORR activity of Pt₃Sc/PECNTs electrocatalyst, investigated by cyclic voltammetry, Rotating Disk electrode (RDE) and Rotating Ring Disk electrode (RRDE), shows the higher mass activity and lower H₂O₂ formation than the commercial catalyst Pt/C-TKK. Accelerated Durability Tests (ADT) was performed to evaluate the stability of catalysts in acidic medium. In single-cell measurements, Pt₃Sc/PECNTs cathode catalyst exhibits a power density of 760 mW cm⁻² at 60 °C. Our study gives an important insight into the design of a novel ORR electrocatalyst with an excellent stability and high power density of PEMFC.     

Binary CuPt alloy nanoparticles assembled on reduced graphene oxide-carbon black hybrid as efficient and cost-effective electrocatalyst for PEMFC

Addressed herein is the synthesis of binary CuPt alloy nanoparticles (NPs), their assembly on reduced graphene oxide (rGO), Vulcan XC72 (VC) and their hybrid (rGO-VC) to be utilized as electrocatalysts for fuel cell reactions (HOR and ORR) in acidic medium and PEMFC tests. The synthesis of nearly-monodisperse Cu₄₅Pt₅₅ alloy NPs was achieved by using a chemical reduction route comprising the reduction of commercially available metal precursors in a hot surfactant solution. As-synthesized Cu₄₅Pt₅₅ alloy NPs were then assembled on three support materials, namely rGO, VC and rGO-VC) via liquid phase self-assembly method. After the characterization, the electrocatalysts were prepared by mixing the yielded materials with Nafion and their electrocatalysis performance was investigated by studying CV and LSV for HOR and ORR in acidic medium. Among the three electrocatalysts tested, Cu₄₅Pt₅₅/rGO-VC hybrid showed the highest catalytic activity with ECSA of 119 m² g⁻¹ and mass activity of 165 mA mg⁻¹_Pt. After the evaluation of electrochemical performance of the three prepared electrocatalysts, their performance was then evaluated in fuel cell conditions. In similar to electrochemical activities, the Cu₄₅Pt₅₅/rGO-VC hybrid electrocatalyst showed a superior fuel cell performance and power output by providing a maximum power of 480 mW cm⁻² with a relatively low Pt loading (0.28 mg cm⁻²). Additionally, the Cu₄₅Pt₅₅/rGO-VC hybrid electrocatalyst exhibited substantially better activity as compared to Pt/rGO-VC electrocatalyst. Therefore, the present study confirmed that alloying Pt with Cu enhances the catalytic activity of Pt metal along with the help of beneficial features of rGO-VC hybrid support material. It should be noted that this is the first example of studying PEMFC performance of CuPt alloy NPs supported on rGO, VC and rGO-VC hybrid.     

PdNi alloy nanoparticles assembled on cobalt ferrite-carbon black composite as a fuel cell catalyst

PdNi alloy nanoparticles (NPs) were synthesized and then readily assembled on the composite of cobalt ferrite NPs with Vulcan XC-72 carbon (CoFe₂O₄-VC). The electrocatalyst performance of the yielded PdNi/CoFe₂O₄-VC composite was tested in borohydride fuel cell reactions in alkaline media. The structure/morphology of colloidal CoFe₂O₄ and PdNi alloy NPs along with the yielded CoFe₂O₄-VC composite and PdNi/CoFe₂O₄-VC electrocatalyst were examined by TEM, powder XRD and ICP-MS. Both monodisperse CoFe₂O₄ and PdNi alloy NPs with 11 and 4 nm average size, respectively, were discernible over the VC support material by the TEM images of the electrocatalyst. The loading ratio of CoFe₂O₄ and PdNi alloy NPs in the composite was found to be 16.1 wt% and 2.7 wt%, respectively, as determined by ICP-MS. The performance of PdNi/CoFe₂O₄-VC as a novel electrocatalyst for oxygen reduction (ORR) and borohydride oxidation (BOR) reactions in alkaline media was studied by voltammetric techniques using a rotating disk electrode. ORR and BOR parameters such as number of exchanged electrons and kinetic current density were calculated. The results revealed that PdNi/CoFe₂O₄-VC electrocatalyst was highly efficient for both ORR and BOR with exchange of 3.2 and 6.6 electrons, respectively.     

Performance of direct methanol fuel cell using carbon nanotube-supported Pt–Ru anode catalyst with controlled composition

The performance of a single-cell direct methanol fuel cell (DMFC) using carbon nanotube-supported Pt–Ru (Pt–Ru/CNT) as an anode catalyst has been investigated. In this study, the Pt–Ru/CNT electrocatalyst was successfully synthesized using a modified polyol approach with a controlled composition very close to 20 wt.%Pt–10 wt.%Ru, and the anode was prepared by coating Pt–Ru/CNT electrocatalyst on a wet-proof carbon cloth substrate with a metal loading of about 4 mg cm⁻². A commercial gas diffusion electrode (GDE) with a platinum black loading of 4 mg cm⁻² obtained from E-TEK was employed as the cathode. The membrane electrode assembly (MEA) was fabricated using Nafion^® 117 membrane and the single-cell DMFC was assembled with graphite endplates as current collectors. Experiments were carried out at moderate low temperatures using 1 M CH₃OH aqueous solution and pure oxygen as reactants. Excellent cell performance was observed. The tested cell significantly outperformed a comparison cell using a commercial anode coated with carbon-supported Pt–Ru (Pt–Ru/C) electrocatalyst of similar composition and loading. High conductivity of carbon nanotube, good catalyst morphology and suitable catalyst composition of the prepared Pt–Ru/CNT electrocatalyst are considered to be some of the key factors leading to enhanced cell performance.     

PdCu bimetallic nanoparticles decorated on ordered mesoporous silica (SBA-15) /MWCNTs as superior electrocatalyst for hydrogen evolution reaction

In the present study, a novel electrocatalyst with excellent catalytic performance based on PdCu bimetallic nanoparticles (NPs) supported on ordered mesoporous silica and multi-walled carbon nanotubes (PdCu NPs/SBA-15-MWCNT) was prepared for electrochemical hydrogen evolution reaction (HER). For this purpose, low-cost mesoporous SBA-15 was synthesized using silica extracted from Stem Sweep Ash (SSA) as an economically attractive silica source. Mesoporous SBA-15 with unparalleled porous structure is a stable support for PdCu bimetallic NPs which prevents the accumulation of PdCu bimetallic NPs and improves its efficiency in the catalytic process. The main advantage of this strategy is low loading of bimetallic catalyst with high catalytic activity. The presence of both mesoporous SBA-15 and MWCNTs materials in PdCu/SBA15-MWCNTs/carbon paste electrode (CPE) increases the metallic active sites and the electrical conductivity of electrode which provides great performance for HER. PdCu/SBA15-MWCNTs-CPE provided small Tafel slope (45 mV dec^?1), low onset potential (~-150 mV), high current density (?165.24 mA cm^?2at -360 mV) and exchange current density (2.51 mA cm^?2) with great durability for HER in H₂SO₄ solution. Analysis of kinetic data suggests that the electrocatalyst controls HER by the Volmer-Heyrovsky mechanism. In addition, studies showed that the presence of sodium dodecyl sulfate (SDS) in electrolyte can decrease the potential of HER and increase the current density.     

Synthesis and characterization of novel high-performance composite electrocatalysts for the oxygen evolution in solid polymer electrolyte (SPE) water electrolysis

Novel Ru_0.3Ir_0.7O₂/Pt_0.15 composite electrocatalysts for the oxygen evolution in solid polymer electrolyte (SPE) water electrolysis were prepared by a two-step method. The intermediate Pt black with or without heat treatment (the final samples marked as C₁ and C₂ respectively) was firstly synthesized by a conventional reduction method with ultrasonic dispersion. The composite electrocatalysts were then prepared by impregnation-reduction method with ultrasonic dispersion followed by fusion treatment. The influence of heat treatment of intermediate Pt black on the properties of the composites was explored. The as-prepared composites were characterized by XRD, BET, SEM, EDX, CV and LP. The catalytic performance of the as-prepared electrocatalysts has also been investigated in a 20 cm² SPE electrolytic cell using Nafion^® 117 as an electrolyte with the loading of noble metals of 1.8 mg cm⁻² at anode and 0.3 mg cm⁻² at cathode. It shows that the catalytic performance of samples C₁ and C₂ is obviously higher than that of commercial PtIrO₂ electrocatalyst and the catalytic activity of C₁ electrocatalyst for the oxygen evolution is evidently higher than that of C₂ electrocatalyst in the whole range of cell voltage. The cell voltage was only 1.76 V and 1.90 V when the current density is 1.0 A cm⁻² and 1.5 A cm⁻² respectively using sample C₁ as anode electrocatalyst.     

Oxygen vacancies and morphology engineered Co3O4 anchored Ru nanoparticles as efficient catalysts for ammonia borane hydrolysis

Developing efficient but facile strategies to modulate the catalytic activity of Ru deposited on metal oxides is of broad interest but remains challenging. Herein, we report the oxygen vacancies and morphological modulation of vacancy-rich Co₃O₄ stabilized Ru nanoparticles (NPs) (Ru/V_O-Co₃O₄) to boost the catalytic activity and durability for hydrogen production from the hydrolysis of ammonia borane (AB). The well-defined and small-sized Ru NPs and V_O-Co₃O₄ induced morphology transformation via in situ driving V_O-Co₃O₄ to 2D nanosheets with abundant oxygen vacancies or Co²⁺ species considerably promote the catalytic activity and durability toward hydrogen evolution from AB hydrolysis. Specifically, the Ru/V_O-Co₃O₄ pre-catalyst exhibits an excellent catalytic activity with a high turnover frequency of 2114 min^?1 at 298 K. Meanwhile, the catalyst also shows a high durability toward AB hydrolysis with six successive cycles. This work establishes a facile but efficient strategy to construct high-performance catalysts for AB hydrolysis.     

Organic ligand-assisted synthesis of Ir0.3Cr0.7O2 solid solution oxides for efficient oxygen evolution in acidic media

Construction of strong interactions between oxides is compelling for modulating the active sites towards acidic oxygen evolution reaction (OER) electrocatalysts. Here, a solid solution oxide electrocatalyst constructed by alloying of IrO₂ and CrO₂ (labeled as Ir_0.3Cr_0.7O₂) is reported with an overpotential of 255 mV at a current density of 10 mA cm^?2 for OER in 0.5 M H₂SO₄ solution, which is much lower than that of the state-of-the-art IrO₂ (357 mV). The mass activity at 1.50 V vs. RHE is 47 folds than that of IrO₂, and it can maintain such OER stability for more than 200 h. Detailed analysis concludes that the organic ligands-assisted synthesis of Ir_0.3Cr_0.7O₂ can enlarge the surface-active area and provide more active sites for water oxidation, while the leaching of Cr and its strong interaction with Ir sites resulting in the formation of high chemical state oxides of Ir with superior activity for acidic OER. It is found that the significantly increasement of oxygen vacancies content during electrochemical test together with the two points mentioned above jointly promote the water oxidation activities of Ir_0.3Cr_0.7O₂ electrocatalyst in acidic media.     

Novel nanorod Ti0·7Ir0·3O2 prepared by facile hydrothermal process: A promising non-carbon support for Pt in PEMFCs

Late transition metal doped TiO₂ has been exploited for generating efficient catalyst support by enhancing electrical conductivity and modifying properties of TiO₂. The Ti_0·7Ir_0·3O₂ nanorod (NRs), a novel catalyst support for Pt nanoparticles, was prepared for the first time via single-step hydrothermal process at low temperature using IrCl₃·3H₂O and TiCl₄ as starting materials. We found that the Ti_0·7Ir_0·3O₂ NRs with 70–80 nm in length and 25–30 nm in width is successful prepared at 210 °C for 12 h without utilizing surfactants or stabilizers. In addition, the Ti_0·7Ir_0·3O₂ NRs was presented principally as a single-phase solid with the TiO₂ is in the rutile form with high crystallinity without using further treatment after synthesis. More importantly, we found that the Ti_0·7Ir_0·3O₂ NRs possesses high electrical conductivity (0.028 S cm⁻¹) dealing the intrinsically non-conducted drawback of TiO₂. The Pt nanoparticles were then deposited on the support of Ti_0·7Ir_0·3O₂ NRs via chemical reduction method. The properties of 20 wt % Pt/Ti_0·7Ir_0·3O₂ NRs electrocatalyst were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), the cyclic voltammetry (CV). The uniformly distributed small Pt nanoparticles (3–4 nm diameter) were well adhered to the Ti_0·7Ir_0·3O₂ NRs. The electrochemically active surface area (ECSA) of 20 wt % Pt/Ti_0·7Ir_0·3O₂ NRs was higher than that of the commercial 20 wt % Pt/C (E-TEK) due to the small size and good dispersion of Pt nanoparticles on the surface of Ti_0·7Ir_0·3O₂ NRs. Moreover, the ECSA value of the Pt/Ti_0·7Ir_0·3O₂ NRs retained up to 88% after 2000 cycles of cyclic voltammetry, suggesting the high stability of catalyst resulted from strong metal support interaction (SMSI) of Titania-based materials with the noble metals. More importantly, the onset potential of Pt/Ti_0·7Ir_0·3O₂ NRs catalyst towards oxygen reduction reaction is more positive (∼80 mV) compared to commercial Pt/C, indicating the high catalytic activity of the Pt/Ti_0·7Ir_0·3O₂ NRs catalyst. The results of this research suggested that novel Ti_0·7Ir_0·3O₂ NRs could be applied as promising robust non-carbon support for Pt. This research also creates a preliminary step for investigating systematically promising Iridium doped Titania materials.     

Boosting activity and stability by coupling Pt–Ni nanoparticles with La-modified flexible carbon nanofibers for hydrogen evolution reaction

Platinum (Pt) is considered as the most efficient catalyst for hydrogen evolution reaction (HER) with a nearly zero overpotential, but it is limited by the high cost and poor stability. Herein, we report an efficient electrocatalyst of Pt–Ni alloy nanoparticles (NPs) supported on the La-modified flexible carbon nanocomposite fibers (PtNi@La-CNFs) for HER. The rare earth metal oxide in the catalyst has a structure-effect relationship with the carbon fibers to form a flexible fiber membrane. Experimental results show that the macroscopic and microscopic properties of carbon nanocomposite fibers can be optimized by doping La₂O₃, and the Pt–Ni NPs can be anchored effectively. The Pt₁Ni₁@La-CNFs electrocatalyst exhibits a small overpotential of 32 mV to achieve current density of 10 mA cm^?2 with a low Tafel slope of 51 mV dec^?1 in alkaline medium, outperforming that of Pt@La-CNFs and the commercial Pt/C catalyst. This study reveals that the multiple coupling effect of rare earth compound, precious metal, and transition metal in composite catalyst can tailor its the electronic configuration, and results in an enhanced HER performance. This work opens up a novel approach to design high active and low cost Pt-based HER catalysts.     

Ultra-fine Ru nanoparticles decorated V2O3 as a pH-universal electrocatalyst for efficient hydrogen evolution reaction

Developing high-efficiency electrocatalysts viable for pH-universal hydrogen evolution reaction (HER) has attracted great interest because hydrogen is a promising renewable energy carrier for replacing fossil fuels. Herein, we present a facile strategy for fabricating ultra-fine Ru nanoparticles (NPs) decorated V₂O₃ on the carbon cloth substrates as efficient and stable pH-universal catalysts for HER. Benefiting from the metallic property and electronic conductivity of V₂O₃ matrix, the optimized hybrid (Ru/V₂O₃-CC) exhibits excellent HER activities in a wide pH range, achieving lower overpotentials of 184, 219, and 221 mV at 100 mA cm⁻² in 0.5 M H₂SO₄, 1.0 M KOH and 1.0 M phosphate-buffered saline, respectively. Moreover, the electrode remains superior stability with negligible degradation after 5000 cyclic voltammetry scanning whether in acidic, alkaline or neutral media. Experimental results, combined with theoretical calculations, demonstrate that the interaction between Ru NPs and the support V₂O₃ induces the local electronic density diversity, allowing optimization of the adsorption energy of Ru towards hydrogen intermediate H1, thus favoring the HER process.     

Performance of membrane electrode assemblies using PdPt alloy as anode catalysts in polymer electrolyte membrane fuel cell

Pd-based nanoparticles, such as 40 wt.% carbon-supported Pd₅₀Pt₅₀, Pd₇₅Pt₂₅, Pd₉₀Pt₁₀ and Pd₉₅Pt₅, for anode electrocatalyst on polymer electrolyte membrane fuel cells (PEMFCs) were synthesized by the borohydride reduction method. PdPt metal particles with a narrow size distribution were dispersed uniformly on a carbon support. The membrane electrode assembly (MEA) with Pd₉₅Pt₅/C as the anode catalyst exhibited comparable single-cell performance to that of commercial Pt/C at 0.7 V. Although the Pt loading of the anode with Pd₉₅Pt₅/C was as low as 0.02 mg cm⁻², the specific power (power to mass of Pt in the MEA) of Pd₉₅Pt₅/C was higher than that of Pt/C at 0.7 V. Furthermore, the single-cell performance with Pd₅₀Pt₅₀/C and Pd₇₅Pt₂₅/C as the anode catalyst at 0.4 V was approximately 95% that of the MEA with the Pt/C catalyst. This indicated that a Pd-based catalyst that has an extremely small amount of Pt (only 5 or 50 at.%) can be replaced as an anode electrocatalyst in PEMFC.