Superior ethylene glycol oxidation electrocatalysis enabled by hollow PdNi nanospheres

Pd-based bimetallic nanosheets for a highly efficient nitrate reduction reaction

The PdNi NS catalyst exhibits outstanding nitrate electroreduction performance, achieving a high NH3 yield rate of 181 μmol h-1 cm-2, a superior FENH3 of 99.6%, and long durability over 20 cycles at -0.77 V (vs. RHE). This work not only introduces a high performance electrocatalyst for ammonia production, but also provides a new perspective on Zn-NO3- batteries.

In situ growth engineering of ultrathin dendritic PdNi nanosheets on nitrogen-doped V2CTx MXenes for efficient hydrogen evolution

Immobilizing metal nanoparticles on a support is crucial for catalysts' stability and spatial distribution. MXenes are promising substrates for in situ growth engineering of various electrocatalysts owing to their merits. A stronger binding capacity can be achieved between the in situ-fabricated catalysts and MXenes compared to a common physical combination. Thus, synergistically utilizing morphology modulation, composition optimization, and the interfacial interaction between metal catalysts and supports will maximize the electrocatalytic activity. However, most reported in situ-formed catalysts on MXenes result in solid 0D nanoparticles and in situ growth of nanoalloy catalysts on MXenes with a precisely controlled morphology is still lacking. Herein, nanodendritic PdNi alloys are in situ grown on nitrogen-doped V2CTx, serving as efficient electrocatalysts toward the hydrogen evolution reaction (HER). Thanks to the synergistic effect of the unique nanodendritic structure of PdNi, the merits of N-TBA-V2CTx nanosheets, and the strong metal-support interaction between the PdNi and the N-TBA-V2CTx support, the in situ-formed Pd58Ni42/N-TBA-V2CTx electrocatalyst shows excellent HER performance with an ultralow overpotential of 44.1 mV to achieve 10 mA cm-2 and a lowest Tafel slope of 39.4 mV dec-1, which outperforms Pd58Ni42/TBA-V2CTx, Pd58Ni42, and Pd/C. Remarkably, the Pd58Ni42/N-TBA-V2CTx catalyst can maintain 92.3% of its initial activity even after 50 h of continuous operation.

Low Pt-Doped Crystalline/Amorphous Heterophase Pd12P3.2 Nanowires as Efficient Catalysts for Methanol Oxidation

Pd-based catalysts are attractive anodic electrocatalysts for direct methanol fuel cells owing to their low cost and natural abundance. However, they suffer from sluggish reaction kinetic and insufficient electroactivity in methanol oxidation reaction (MOR). In this work, we developed a facile one-pot approach to fabricate low Pt-doped Pd₁₂P_3.2 nanowires with crystalline/amorphous heterophase (termed Pt-Pd₁₂P_3.2 NWs) for MOR. The unique crystalline/amorphous heterophase structures promote the catalytic activity by the plentiful active sites at the phase boundaries and/or interfaces and the synergistic effect between different phases. Moreover, the incorporation of trace Pt into Pd lattices modifies the electronic structure and improves the electron transfer ability. Therefore, the obtained Pt-Pd₁₂P_3.2 NWs display significantly enhanced electrocatalytic performance toward MOR with the mass activity of 2.35 A mg_Pd+Pt^-1, which is 9.0, 2.9, and 2.0 times higher than those of the commercial Pd/C (0.26 A mg_Pd^-1), Pd₁₂P_3.2 NWs (0.82 A mg_Pd^-1), and commercial Pt/C (1.19 A mg_Pt^-1). The high mass activity enables the Pt-Pd₁₂P_3.2 NWs to be the promising Pd-based catalysts for MOR.

Fabrication of cobaltous telluride and carbon composite as a promising carrier for boosting electro oxidation of ethylene glycol on palladium in alkaline medium

The development of highly active and earth-rich electrocatalysts remains a formidable challenge for the commercialization of fuel cells. Herein, a composite carrier composed of cobaltous telluride (CoTe) and carbon (C) has been designed for the first time to enhance the electrocatalytic performance of palladium (Pd) nanoparticles (NPs) for the electro-oxidation of ethylene glycol (EG). Remarkably, the mass activity for the as-prepared Pd/CoTe-C catalyst during the ethylene glycol oxidation reaction (EGOR) is found to reach up to 3917.3 mA mg^-1, which is 2.2 times higher than that of Pd/Co-C (1785.0 mA mg^-1) and 4.1 times greater than that of commercial Pd/C catalyst (962.4 mA mg^-1), exceeding that obtained for most Pd-based electrocatalysts reported thus far. In particular, the Pd/CoTe-C catalyst shows better electrochemical stability toward the EGOR than the Pd/Co-C and commercial Pd/C catalysts. Thus, the Pd/CoTe-C electrocatalyst is expected to exhibit broad application prospects in the field of fuel cells.

Surfactant-free synthesis of carbon-supported silver (Ag/C) nanobars as an efficient electrocatalyst for alcohol tolerance and oxidation of sodium borohydride in alkaline medium

We have synthesized carbon-supported silver (Ag/C) nanobars by a simple surfactant-free hydrothermal method using glucose as the reducing reagent as well as the source of carbon in Ag/C nanobars. Physicochemical characterization of the materials was performed by X-ray Diffraction (XRD), field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The XRD pattern confirmed the presence of a pure metallic silver phase. No carbon phase was detected, which indicates that the carbon exists mainly in the amorphous form. The electrocatalytic activity of Ag/C in different electrolyte solutions such as 0.5 M NaOH, 0.5 M NaOH + 1 M ethanol (EtOH), 0.5 M NaOH + 1 M ethylene glycol (EG), and 0.5 M NaOH + 0.01 M NaBH4 (sodium borohydride) was studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA) study. Alcohol tolerance of the catalysts was also established in the presence of ethanol and ethylene glycol. The forward-to-backward current ratio from cyclic voltammetry (CV) study of Ag/C-20 (20 h) in 0.5 M NaOH + 1 M ethanol solution at 100 mV s−1 scan rate is 4.13 times higher compared to that of Ag/C-5 (5 h). Hence, Ag/C-20 is a better candidate for the tolerance of ethanol. In the presence of ethylene glycol (1 M) in 0.5 M NaOH solution, it is obtained that the forward-to-backward current ratio at the same scan rate for Ag/C-20 is lower than that in the presence of ethanol. The durability of the catalyst was studied by chronoamperometry measurement. We studied the electrochemical kinetics of Ag/C catalysts for borohydride oxidation in an alkaline medium. The basic electrochemical results for borohydride oxidation show that Ag/C has very well strength and activity for direct borohydride oxidation in an alkaline medium. The reaction of borohydride oxidation with the contemporaneous BH4−. hydrolysis was noticed at the oxidized silver surface. Among all the synthesized Ag/C catalysts, Ag/C-20 exhibited the best electrocatalytic performance for borohydride oxidation in an alkaline medium. The activation energy and the number of exchange electrons at Ag/C-20 electrode surface for borohydride electro-oxidation were estimated as 57.2 kJ mol−1 and 2.27, respectively.

Mesoporous Pt@PtM (M = Co, Ni) cage-bell nanostructures toward methanol electro-oxidation

Rational design of Pt-based nanostructures with a controllable morphology and composition is vital for electrocatalysis. Herein, we demonstrate a dual-template strategy to fabricate well-defined cage-bell nanostructures including a Pt core and a mesoporous PtM (M = Co, Ni) bimetallic shell (Pt@mPtM (M = Co, Ni) CBs). Owing to their unique nanostructure and bimetallic properties, Pt@mPtM (M = Co, Ni) CBs show higher catalytic activity, better durability and stronger CO tolerance for the methanol oxidation reaction than commercial Pt/C. This work provides a general method for convenient preparation of cage-bell nanostructures with a mesoporous bimetallic shell, which have high promising potential for application in electrocatalytic fields.