Abstract
Replacing sluggish oxygen evolution reaction (OER) with hydrazine oxidation reaction (HzOR) to produce hydrogen has been considered as a more energy-efficient strategy than water splitting. ...However, the relatively high cell voltage in two-electrode system and the required external electric power hinder its scalable applications, especially in mobile devices. Herein, we report a bifunctional P, W co-doped Co
3
N nanowire array electrode with remarkable catalytic activity towards both HzOR (−55 mV at 10 mA cm
−2
) and hydrogen evolution reaction (HER, −41 mV at 10 mA cm
−2
). Inspiringly, a record low cell voltage of 28 mV is required to achieve 10 mA cm
−2
in two-electrode system. DFT calculations decipher that the doping optimized H* adsorption/desorption and dehydrogenation kinetics could be the underlying mechanism. Importantly, a self-powered H
2
production system by integrating a direct hydrazine fuel cell with a hydrazine splitting electrolyzer can achieve a decent rate of 1.25 mmol h
−1
at room temperature.
Metal–organic frameworks (MOFs) have attracted tremendous interest due to their promising applications including electrocatalysis originating from their unique structural features. However, it ...remains a challenge to directly use MOFs for oxygen electrocatalysis because it is quite difficult to manipulate their dimension, composition, and morphology of the MOFs with abundant active sites. Here, a facile ambient temperature synthesis of unique NiCoFe‐based trimetallic MOF nanostructures with foam‐like architecture is reported, which exhibit extraordinary oxygen evolution reaction (OER) activity as directly used catalyst in alkaline condition. Specifically, the (Ni2Co1)0.925Fe0.075‐MOF‐NF delivers a minimum overpotential of 257 mV to reach the current density of 10 mA cm−2 with a small Tafel slope of 41.3 mV dec−1 and exhibits high durability after long‐term testing. More importantly, the deciphering of the possible origination of the high activity is performed through the characterization of the intermediates during the OER process, where the electrochemically transformed metal hydroxides and oxyhydroxides are confirmed as the active species.
Hierarchical trimetallic NiCoFe‐based metal–organic framework (MOF) nanofoam with modulated molar ratios is successfully synthesized through a developed mild, onepot, ambient‐temperature, solution‐phase method. The nanofoam can be directly utilized as an efficient oxygen evolution reaction (OER) catalyst with extraordinary activity and excellent durability. The metal hydroxide and oxyhydroxide evolved from the pristine MOF structure are demonstrated as the active species for high OER activity.
Mesoporous NiCo2O4 nanosheets can be directly grown on various conductive substrates, such as Ni foam, Ti foil, stainless‐steel foil and flexible graphite paper, through a general template‐free ...solution method combined with a simple post annealing treatment. As a highly integrated binder‐ and conductive‐agent‐free electrode for supercapacitors, the mesoporous NiCo2O4 nanosheets supported on Ni foam deliver ultrahigh capacitance and excellent high‐rate cycling stability.
Strongly coupled NiCo2O4‐rGO hybrid nanosheets are syntheiszed through a cost‐effective two‐step strategy involving a facile polyol process and subsequent thermal annealing treatment in air. The ...hybrid nanosheets exhibit impressive electrocatalytic performance for the oxygen reduction reaction (ORR) with a current density and onset potential comparable to those of commercial Pt/C catalyts, while having perfect tolerance to methanol..
Two one-dimensional hierarchical hybrid nanostructures composed of NiCo2O4 nanorods and ultrathin nanosheets on carbon nanofibers (CNFs) are controllably synthesized through facile solution methods ...combined with a simple thermal treatment. The structure of NiCo2O4 can be easily controlled to be nanorods or nanosheets by using different additives in the synthesis. These two different nanostructures are evaluated as electrodes for high performance supercapacitors, in view of their apparent advantages, such as high electroactive surface area, ultrathin and porous features, robust mechanical strength, shorter ion and electron transport path. Their electrochemical performance is systematically studied, and both of these two hierarchical hybrid nanostructures exhibit high capacitance and excellent cycling stability. The remarkable electrochemical performance will undoubtedly make these hybrid structures attractive for high-performance supercapacitors with high power and energy densities.
Hierarchical tubular structures constructed by ultrathin carbon‐coated SnO2 nanoplates are rationally designed and synthesized. This interesting structure simultaneously integrates the structural and ...compositional design rationales for high‐energy anode materials based on low‐dimensional ultrathin nanoplates, a hollow tubular structure, and a carbon nanocoating. When evaluated as an anode material for lithium‐ion batteries, the as‐synthesized SnO2‐carbon hybrid structure manifests high specific capacity and excellent cycling stability.
The surface morphology of Li metal anode significantly dictates the stability and safety of Li metal batteries. The key parameters for morphological control and causes for dendritic growth of Li ...anode are still not clear. Although the plating kinetics is generally believed to be associated with Li growth habits, the detailed models are still not well defined. In this work, the temperature effect on the stability and efficiency of Li anode is systematically investigated in a variety of electrolyte composition for Li metal batteries. A dendrite‐free growth mechanism is observed, and a high Coulombic efficiency up to ≈99.4% in Li||Cu cells is achieved by tuning the deposition behaviors at elevated temperatures. The results provide insights into the Li dendrite growth mechanism and general principle for developing stable Li anode.
The temperature effect on lithium metal anodes is demonstrated in a variety of aprotic electrolytes. High Coulombic efficiency and dendrite‐free growth modes can be achieved in an ether‐based electrolyte at elevated temperature. The electrochemical kinetics of lithium plating/stripping processes are significantly improved at high temperature.
Improvement in power conversion efficiency has been observed in cadmium selenide nanorods/poly(3-hexylthiophene) hybrid solar cells through benzene-1,3-dithiol chemical vapor annealing. Phosphor NMR ...studies of the nanorods and TEM/AFM characterizations of the morphology of the blended film showed that the ligand exchange reaction and related phase separation happening during the chemical vapor annealing are responsible for the performance enhancement.
Abstract The carbon−carbon coupling at the Cu/Cu 2 O Schottky interface has been widely recognized as a promising approach for electrocatalytic CO 2 conversion into value-added alcohols. However, the ...limited selectivity of C 2+ alcohols persists due to the insufficient control over rectifying interface characteristics required for precise bonding of oxyhydrocarbons. Herein, we present an investigation into the manipulation of the coordination environment of Cu sites through an in-situ electrochemical reconstruction strategy, which indicates that the construction of low-coordinated Cu sites at the Cu/Cu 2 O interface facilitates the enhanced rectifying interfaces, and induces asymmetric electronic perturbation and faster electron exchange, thereby boosting C-C coupling and bonding oxyhydrocarbons towards the nucleophilic reaction process of *H 2 CCO-CO. Impressively, the low-coordinated Cu sites at the Cu/Cu 2 O interface exhibit superior faradic efficiency of 64.15 ± 1.92% and energy efficiency of ~39.32% for C 2+ alcohols production, while maintaining stability for over 50 h (faradic efficiency >50%, total current density = 200 mA cm −2 ) in a flow-cell electrolyzer. Theoretical calculations, operando synchrotron radiation Fourier transform infrared spectroscopy, and Raman experiments decipher that the low-coordinated Cu sites at the Cu/Cu 2 O interface can enhance the coverage of *CO and adsorption of *CH 2 CO and CH 2 CHO, facilitating the formation of C 2+ alcohols.
A rational yet scalable solution phase method has been established, for the first time, to obtain n-type Bi2Te3 ultrathin nanowires with an average diameter of 8 nm in high yield (up to 93%). ...Thermoelectric properties of bulk pellets fabricated by compressing the nanowire powder through spark plasma sintering have been investigated. Compared to the current commercial n-type Bi2Te3-based bulk materials, our nanowire devices exhibit an enhanced ZT of 0.96 peaked at 380 K due to a significant reduction of thermal conductivity derived from phonon scattering at the nanoscale interfaces in the bulk pellets, which corresponds to a 13% enhancement compared to that of the best n-type commercial Bi2Te2.7Se0.3 single crystals (∼0.85) and is comparable to the best reported result of n-type Bi2Te2.7Se0.3 sample (ZT = 1.04) fabricated by the hot pressing of ball-milled powder. The uniformity and high yield of the nanowires provide a promising route to make significant contributions to the manufacture of nanotechnology-based thermoelectric power generation and solid-state cooling devices with superior performance in a reliable and a reproducible way.
PDF
