Zhijun Jia

A membrane-less Na ion battery-based CAPMIX cell for energy extraction using water salinity gradients

“Salinity energy” stored as the salinity difference between sea water and fresh water is a large scale renewable resource that can be harvested and converted to electricity directly. In this study, a high performance membrane-less Na ion battery-based “capacitive mixing” cell (CAPMIX) was fabricated to extract the entropy energy from the water salinity gradient. The CAPMIX used copper hexacyanoferrate and silver as the electrodes in an aqueous electrolyte. A maximum working voltage of 0.65 V and a maximum power output of 2798 μW g−1 was obtained, which is a significant improvement over previous reported results. This energy harvesting process does not seem to play any significant role in the natural process and no deleterious substances were added to the output stream; it is a completely environmentally friendly power source. The entropy energy extracting battery represents a novel electrochemical device and is also a promising technology in the development of renewable energy production.

Hierarchical Ni–Fe layered double hydroxide/MnO2 sphere architecture as an efficient noble metal-free electrocatalyst for ethanol electro-oxidation in alkaline solution

Ni–Fe layered double hydroxide (LDH) nanosheets and hierarchical Ni–Fe LDH@MnO2 spheres are synthesized by a facile and cost-effective approach for highly efficient ethanol electro-oxidation. The LDH@MnO2 microspheres display excellent catalytic activity and robust durability for ethanol electro-oxidation, compared with the Ni–Fe LDH nanosheets. According to the analyses for nitrogen adsorption isotherms and electrochemical impedance spectra (EIS), it is inferred that the performance enhancement could be attributed to the MnO2 increasing the concentration of OHads species on the Ni–Fe LDH surface. These OHads can react with C1ad intermediate species to produce CO2 or water soluble products, releasing the active sites on LDH for further electrochemical reactions. Therefore, it is expected that an effective noble-metal free catalyst for ethanol electro-oxidation could be obtained by tailoring structure and properties of LDHs and their composites.

Electrochemical sodium storage of copper hexacyanoferrate with a well-defined open framework for sodium ion batteries

Sodium ion batteries are considered to be a promising low-cost alternative to common lithium batteries. The exploration of new electrode materials is extremely important for developing sodium ion batteries. In this work, copper hexacyanoferrate (CuHCF), a kind of Prussian blue analogue, was synthesized by a chemical co-precipitation method and the feasibility of the electrochemical sodium ion storage reaction in CuHCF nano-particles in aqueous solution was investigated. All the results demonstrate that the sodium ions can be reversibly inserted/extracted into/from CuHCF nano-particles in aqueous solution, and a specific capacity of 46 mA h g−1 is obtained at the current density of 20 mA g−1. The sodium ion insertion and extraction behaviors are controlled by the solid phase diffusion process in the CuHCF electrode. The well-defined open framework of CuHCF ensures it has good cycle stability. The good performance indicates that CuHCF will be a promising candidate for the cathode materials of sodium ion batteries.

Pd nanoparticles supported on Mg–Al–CO3 layered double hydroxide as an effective catalyst for methanol electro-oxidation

Pd/C and Pd/Mg–Al–CO3 LDH (Pd/LDH) catalysts were prepared and their catalytic performances for methanol electro-oxidation in alkaline solution were investigated in this work. The result of cyclic voltammograms proves that Pd/LDH has a much higher specific activity than Pd/C. CO stripping results indicate that Mg–Al–CO3 LDH could facilitate the oxidative removal of adsorbed CO and improve the CO poison resistance of Pd/LDH catalysts. The chronoamperograms also indicate that Pd/LDH has a better stability. All the results imply that Pd/LDH is very promising for probable application in the DMFC field. Furthermore, the insight for the increase of the specific activity is discussed in this work.

Hierarchical porous nitrogen doped reduced graphene oxide prepared by surface decoration–thermal treatment method as high-activity oxygen reduction reaction catalyst and high-performance supercapacitor electrodes

Nitrogen doped (N-doped) porous reduced graphene oxide (rGO) is successfully obtained by a two-step method, which includes a surface finishing of graphene oxide (GO) followed by thermal treatment. Distinct from many other methods, such as heat treatment, chemical vapor deposition or plasma treatment, a special atmosphere (NH3) and special equipment is avoided using this method. The nitrogen atoms are introduced into the reduced graphene oxide by this method according to the X-ray photoelectron spectroscopy (XPS) results. Based on the high specific surface area, high porosity, and doped heteroatoms, the as-prepared N-doped reduced graphene oxide shows excellent electrocatalytic activity towards the oxygen reduction reaction (ORR) and high capacitance, compared with a pristine reduced graphene oxide sample. Therefore, this work demonstrates a good example of both electrocatalytic activity and capacitance properties of N-doped reduced graphene oxide prepared by the surface decoration of GO followed by heat treatment method, which opens the door for creating functional graphene materials with highly promising applications in high-performance renewable energy conversion and storage devices.

Novel palladium–yttrium (Pd–Y/C) catalysts for methanol electrooxidation in alkaline media

Carbon black supported bimetallic palladium–yttrium (Pd-Y/C) catalysts with different Pd–Y ratios were prepared by chemical reduction and calcination treatment methods. Electrochemical characterization techniques, including cyclic voltammetry (CV), chronoamperometry (CA), and CO stripping were carried out to analyze the electrochemical performance of these catalysts for methanol oxidation in alkaline media. All the results show that the 20%Pd–5.0%Y/C catalyst has a higher catalytic activity than the 20%Pd/C catalyst, and the addition of Y also facilitates the oxidative removal of adsorbed CO. The promoting effect of Y is explained by a bifunctional mechanism.

Novel palladium-gadolinium (Pd-Gd/C) bimetallic catalysts for electrooxidation of methanol in alkaline media

Pd/C and Pd-Gd/C catalysts were synthesized and their catalytic performance for methanol electrooxidation in alkaline solution was compared. The structure, morphology and nature of surface species of these catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and CO stripping results show that the 20%Pd-10%Gd/C catalyst has better electrocatalytic activity and durability, as well as higher resistance to CO poisoning than that of the 20%Pd/C catalyst. Furthermore, the insight for the promoting effect of Gd on the specific activity is discussed in this work.

High-performance aqueous rechargeable batteries based on zinc anode and NiCo2O4 cathode

A new aqueous Zn-NiCo2O4 rechargeable battery system with a high voltage, consisting of NiCo2O4 as cathode and metal Zn as anode, is proposed for the first time. It is cheap and environmental friendly, and its energy density is about 202.8 Wh kg −1. The system still maintains excellent capacity retention of about 85% after 100 full cycles at a current rate of 2 A g −1 between 1.5 and 1.95 V. This work not only provides a new battery system but also shows promise for application in large-scale energy storage for its low cost, good cycling and environmental friendliness.