Synthesis of a MoS x -O-PtO x Electrocatalyst with High Hydrogen Evolution Activity Using a Sacrificial Counter-Electrode.

Water splitting is considered to be a very promising alternative to greenly produce hydrogen, and the key to optimizing this process is the development of suitable electrocatalysts. Here, a sacrificial-counter-electrode method to synthesize a MoS x /carbon nanotubes/Pt catalyst (0.55 wt% Pt loading) is developed, which exhibits a low overpotential of 25 mV at a current density of 10 mA cm-2, a low Tafel slope of 27 mV dec-1, and excellent stability under acidic conditions. The theory calculations and experimental results confirm the high hydrogen evolution activity that is likely due to the fact that the S atoms in MoS x can be substituted with O atoms during a potential cycling process when using Pt as a counter-electrode, where the O atoms act as bridges between the catalytic PtO x particles and the MoS x support to generate a MoS x -O-PtO x structure, allowing the Pt atoms to donate more electrons thus facilitating the hydrogen evolution reaction process.

3D CNTs/Graphene-S-Al3Ni2 Cathodes for High-Sulfur-Loading and Long-Life Lithium-Sulfur Batteries.

Lithium-sulfur batteries suffer from poor cycling stability at high areal sulfur loadings (ASLs) mainly because of the infamous shuttle problem and the increasing diffusion distance for ions to diffuse along the vertical direction of the cathode plane. Here, a carbon nanotube (CNT)/graphene (Gra)-S-Al3Ni2 cathode with 3D network structure is designed and prepared. The 3D network configuration and the Al in the Al3Ni2 provide an efficient channel for fast electron and ion transfer in the three dimensions, especially along the vertical direction of the cathode. The introduction of Ni in the Al3Ni2 is able to suppress the shuttle effect via accelerating reaction kinetics of lithium polysulfide species conversion reactions. The CNT/Gra-S-Al3Ni2 cathode exhibits ultrahigh cycle-ability at 1 C over 800 cycles, with a capacity degradation rate of 0.055% per cycle. Additionally, having high ASLs of 3.3 mg cm-2, the electrode delivers a high reversible areal capacity of 2.05 mA h cm-2 (622 mA h g-1) over 200 cycles at a higher current density of 2.76 mA cm-2 with high capacity retention of 85.9%. The outstanding discharge performance indicates that the design offers a promising avenue to develop long-life cycle and high-sulfur-loading Li-S batteries.

Highly efficient oxygen evolution from CoS2/CNT nanocomposites via a one-step electrochemical deposition and dissolution method.

The oxygen evolution reaction (OER) has been viewed as a critical step in electrochemical energy conversion and storage devices. However, searching for cheap and efficient OER electrocatalysts still remains an urgent task. Herein, we develop a new strategy involving a one-step electrochemical deposition and dissolution method to fabricate hydrophilic porous CoS2/carbon nanotube (CNT) composites (CNT-CoS2). X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy measurements confirm the formation of hydrophilic groups on the surface of the porous CoS2 during electrochemical oxidation. Our design holds several advantages. The electricity conductivity of CoS2 is increased by introducing CNTs as a conductive substrate. The porous nanostructures of CoS2 increase its surface area, and provide paths to promote charge and reactant transfer. The active edge sites modified with hydrophilic groups can increase the content of electrolyte-electrode contact points, increasing the intrinsic catalytic performance of CoS2. These factors allow CNT-CoS2 to achieve a low onset potential of 1.33 V vs. RHE, a stable current density (j) of 10 mA cm-2 at an overpotential of 290 mV, and excellent stability under alkaline conditions compared to that of IrO2. The comprehensive performance of the CNT-CoS2 electrocatalyst is comparable to or better than that of any reported noble metal-free OER catalyst, even RuO2 and IrO2. This facile synthesis strategy involving synchronous electrochemical deposition and dissolution should be easily adapted for large-scale water electrolysis.

Neuron-Inspired Interpenetrative Network Composed of Cobalt-Phosphorus-Derived Nanoparticles Embedded within Porous Carbon Nanotubes for Efficient Hydrogen Production.

The ongoing search for cheap and efficient hydrogen evolution reaction (HER) electrocatalysts to replace currently used catalysts based on Pt or its alloys has been considered as an prevalent strategy to produce renewable and clean hydrogen energy. Herein, inspired by the neuron structure in biological systems, we demonstrate a novel fabrication strategy via a simple two-step method for the synthesis of a neuronlike interpenetrative nanocomposite network of Co-P embedded in porous carbon nanotubes (NIN-Co-P/PCNTs). It is found that the interpenetrative network provides a natural transport path to accelerate the hydrogen production process. The embedded-type structure improves the utilization ratio of Co-P and the hollow, tubelike, and porous structure of PCNTs further promote charge and reactant transport. These factors allow the as-prepared NIN-Co-P/PCNTs to achieve a onset potential low to 43 mV, a Tafel slope as small as 40 mV/decade, an excellent stability, and a high turnover frequency value of 3.2 s(-1) at η = 0.2 V in acidic conditions. These encouraging properties derived from the neuronlike interpenetrative network structure might offer new inspiration for the preparation of more nanocomposites for applications in other catalytic and optoelectronic field.

Subnanometer Molybdenum Sulfide on Carbon Nanotubes as a Highly Active and Stable Electrocatalyst for Hydrogen Evolution Reaction.

Electrochemically splitting water for hydrogen evolution reaction (HER) has been viewed as a promising approach to produce renewable and clean hydrogen energy. However, searching for cheap and efficient HER electrocatalysts to replace the currently used Pt-based catalysts remains an urgent task. Herein, we develop a one-step carbon nanotube (CNT) assisted synthesis strategy with CNTs' strong adsorbability to mediate the growth of subnanometer-sized MoS(x) on CNTs. The subnanometer MoS(x)-CNT hybrids achieve a low overpotential of 106 mV at 10 mA cm(-2), a small Tafel slope of 37 mV per decade, and an unprecedentedly high turnover frequency value of 18.84 s(-1) at η = 200 mV among all reported non-Pt catalysts in acidic conditions. The superior performance of the hybrid catalysts benefits from the presence of a higher number of active sites and the abundant exposure of unsaturated S atoms rooted in the subnanometer structure, demonstrating a new class of subnanometer-scale catalysts.