Jiahui Chen

Hollow PdCo alloy nanospheres with mesoporous shells as high-performance catalysts for methanol oxidation

Monodisperse hollow mesoporous PdCo alloy nanospheres are prepared via a simple galvanic replacement reaction. The as-prepared PdCo hollow nanospheres have small diameter, such as Pd78Co22 nanospheres of diameter about 25u202fnm and mesoporous shells about 4-5u202fnm. The Pd78Co22 hollow mesoporous nanospheres possess the largest electrochemical active surface areas (ECSA, 53.91u202fm2u202fg-1), mass activity (1488u202fmAu202fmg-1) and specific activity (2.76u202fmAu202fcm-2) towards to methanol oxidation relative to the Pd68Co32, Pd92Co8 hollow mesoporous nanospheres and commercial Pd/C catalysts. Moreover, the activity of Pd78Co22 after long-term stability tests is still the best and even better than those of fresh Pd68Co32 and commercial Pd/C catalysts. The PdCo catalysts not only effectively reduce the Pd usage by forming hollow structure, but also fully realize the Pd-Co alloying effects for enhancing the methanol oxidation catalytic performance.

Iron‐Doped Nickel Phosphide Nanosheets In Situ Grown on Nickel Submicrowires as Efficient Electrocatalysts for Oxygen Evolution Reaction

Tens of micrometers long metallic Ni submicrowires with a diameter of approximately 200u2005nm are prepared by a chemical reduction method under a magnetic field. Fe‐doped Ni2P nanosheets are then inu2005situ grown on Ni submicrowires by a simple wet‐chemical reaction followed by a low‐temperature phosphorization process. The (Ni0.87Fe0.13)2P–Ni composite exhibits the highest catalytic activity toward oxygen evolution reaction in alkaline solution among all the as‐prepared (Ni1−xFex)2P–Ni catalysts, delivering a current density of 10u2005mAu2009cm−2 at an overpotential of only 257u2005mV and keeping high stability over 10u2005h electrolysis. These exceptional activities are attributed to the unique structure combining metallic Ni submicrowires as good electronically conductive substrate and the inu2005situ grown Fe‐doped Ni2P nanosheets. Specifically, Fe incorporation leads to strong electron interactions between Ni, Fe, and P, fast reaction kinetics, small charge‐transfer resistance, and a large electrochemical surface area, which are responsible for the excellent catalytic performance.

Tubular Cu(OH)2 arrays decorated with nanothorny Co–Ni bimetallic carbonate hydroxide supported on Cu foam: a 3D hierarchical core–shell efficient electrocatalyst for the oxygen evolution reaction

Developing highly efficient and low-cost oxygen evolution reaction (OER) electrocatalysts is highly demanded, as the OER is recognized as a key half-reaction in water splitting for producing hydrogen; however, this still remains a great challenge. Herein, we design three-dimensional (3D) tubular hierarchical core–shell electrocatalysts for the OER using a simple and highly controllable two-step method. The large-scale tubular Cu(OH)2 arrays are directly grown on Cu foam (CF) at room temperature, followed by the growth of highly porous CoNi carbonate hydroxides (CH) via a low-temperature hydrothermal method on the walls of these Cu(OH)2 nanotubes (NTs). The hollow and open-structured core–shell hierarchical Cu(OH)2@CoNiCH NTs/CF electrode with a large surface area and numerous mesoporous and short diffusion paths can provide many active sites, fast electron transport and easy accessibility of water, leading to an excellent OER activity in an alkaline electrolyte with an overpotential of 288 mV and 326 mV at a current density of 30 mA cm−2 and 100 mA cm−2, respectively, also with robust durability. This new structure would open an avenue for the advancement of highly efficient OER electrocatalysts.

Electroless Deposition Metals on Poly(dimethylsiloxane) with Strong Adhesion As Flexible and Stretchable Conductive Materials

A new surface modification method is developed for electroless deposition of robust metal (copper, nickel, silver) layers on poly(dimethylsiloxane) (PDMS) substrate with strong adhesion. Under the synergies of the polydopamine (PDA), the plasma process enhances Ag+ reduction, and a thin Ag film is capable of tightly attaching to the PDMS surface, which catalyzes electroless deposition (ELD) to form robust metal layers on the PDMS surface with strong adhesion. Subsequently, a flexible and stretchable Cu-PDMS conductor is obtained through this method, showing excellent metallic conductivity of 1.2 × 107 S m-1, even at the longest stretch strain (700%). This process provides a successful strategy for obtaining good robust metal layers on PDMS and other polymer substrate surfaces with strong adhesion and conductivity.

Enhanced Li ion conductivity in Ge-doped Li0.33La0.56TiO3 perovskite solid electrolytes for all-solid-state Li-ion batteries

Ge-Doped Li0.33La0.56TiO3 (Ge-LLTO) perovskites are synthesized with various GeO2 contents by solid-state reactions as Li-ion conductive electrolytes for rechargeable all-solid-state Li batteries. After the addition of GeO2, the sinterability and Li ion conductivity are enhanced for the perovskite solid electrolyte. The Li0.43La0.56Ti0.95Ge0.05O3 electrolytes exhibit the highest sinterability and Li ion conductivity among the as-prepared Li0.33+2xLa0.56Ti1−xGexO3 electrolytes. The improvement of Li ion conductivity might be attributed to the improvement of the densification and structural integrity of the LLTO solid electrolyte. The lithium transference number (tLi+) of Ge-doped LLTO is close to 1. Moreover, the Ge-LLTO electrolytes are stable in the potential range of 0–10 V vs. Li/Li+.

PdCu alloy nanoparticles supported on reduced graphene oxide for electrocatalytic oxidation of methanol

PdCu nanoparticles supported on reduced graphene oxide nanosheets (PdCu/rGO) with uniform size distribution and dispersion are fabricated by a facile two-step reduction method. During the whole synthesis procedure, no capping agent or surfactant has been used. By varying the Pd/Cu molar ratio, electrocatalysts with different size distribution and dispersion of nanoparticles on graphene are prepared, and their electrocatalytic performance toward methanol oxidation reaction has been studied. It is concluded that the as-prepared electrocatalyst of Pd2Cu2/rGO, of which the Pd/Cu molar ratio is 1:1, exhibits the highest mass activity and most stable electroactivity. Compared to commercial Pd/C, the as-prepared Pd2Cu2/rGO also demonstrates 2.49 times higher mass activity and much more stable electroactivity. The excellent performance of the Pd2Cu2/rGO electrocatalyts is mainly due to the advantages of bimetallic synergistic effects and the supporting material of graphene. Owing to the advantages of high electroactivity, long stability, and cost-effectiveness, the as-prepared Pd2Cu2/rGO nanocomposites are promising anode electrocatalysts for direct methanol fuel cells.

Flowerlike NiCo2S4 Hollow Sub-Microspheres with Mesoporous Nanoshells Support Pd Nanoparticles for Enhanced Hydrogen Evolution Reaction Electrocatalysis in Both Acidic and Alkaline Conditions

Flowerlike NiCo2S4 hollow sub-microspheres are synthesized through Cu2O templates to support Pd nanoparticles as high-efficiency catalysts for the hydrogen evolution reaction (HER). The diameter and shell size of NiCo2S4 hollow sub-microspheres are about 400 and 16 nm, respectively. In addition, the surface of the shells is constructed by petallike nanosheets. About 3 nm Pd particles uniformly incorporate with the flowerlike NiCo2S4 hollow sub-microsphere to form the NiCo2S4/Pd heterostructure. The NiCo2S4/Pd catalysts exhibit significantly lower overpotential of only 87 and 83 mV at 10 mA/cm2 for the HER in both acidic and alkaline conditions, respectively, relative to NiCo2S4 (247, 226 mV) and Pd (175, 385 mV) catalysts. Besides, the NiCo2S4/Pd catalysts also exhibit excellent stability of HER in these two conditions. The superior HER performance of NiCo2S4/Pd might be resulted from the unique architecture of metal nanoparticles anchored on the bimetallic sulfide flowerlike hollow sub-microspheres, which could provide high surface area, lots of active sites, strong synergetic effect, and stable structure.

Hollow PdCu alloy catalysts for electroless copper/nickel deposition

We used a facile method to prepare PdCu hollow nanocubes (HNCs) and nanospheres (HNSs) for electroless copper or nickel deposition by via redox reaction with the sacrificial templates of Cu2O. The electrocatalytic performance of PdCu HNSs is higher than PdCu HNCs through CV and EQCM tests. Also, PdCu HNSs was applied to electroless copper and nickel deposition, and find that the quite low concentration up to 1 mM and 2 mM of PdCu alloy for electroless copper and nickel deposition still has the good catalytic performance, respectively.