Minghua Huang

A simple route to incorporate redox mediator into carbon nanotubes/ Nafion composite film and its application to determine NADH at low potential

Through a new and simple ion-exchange route, two-electron redox mediator thionine has been deliberately incorporated into the carbon nanotubes (CNTs)/Nafion composite film due to the fact that there is strong interaction between any of two among the three materials (ion-exchange process between thionine and Nafion, strong adsorption of thionine by CNTs, and wrapping and solubilizing of CNTs with Nafion). The good homogenization of electron conductor CNTs in the integrated films provides the possibility of three-dimensional electron conductive network. The resulting integrated films exhibited high and stable electrocatalytic activity toward NADH oxidation with the significant decrease of high overpotential, which responds more sensitively more than those modified by thionine or CNTs alone. Such high electrocatalytic activity facilitated the low potential determination of NADH (as low as -0.1 V), which eliminated the interferences from other easily oxidizable species. In a word, the immobilization approach is very simple, timesaving and effective, which could be extended to the immobilization of other cationic redox mediators into the CNTs/Nafion composite film. And these features may offer potential promise for the design of amperometric biosensors.

An electrodeposited cobalt–selenide-based film as an efficient bifunctional electrocatalyst for full water splitting

Design and development of noble metal-free, active and bifunctional electrocatalysts is crucial for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the full water splitting process. Herein, an amorphous cobalt–cobalt oxide/cobalt selenide composite film (CoOx–CoSe) has been fabricated directly on a three-dimensional macro-porous Ni foam (NF) substrate by a facile electrodeposition method, which shows remarkable activity and good long-term stability as an efficient bifunctional electrocatalyst for the OER and HER under alkaline conditions. In 1.0 M KOH, this catalyst as a robust 3D O2-evolving anode can achieve 100 mA cm−2 and 500 mA cm−2 only at overpotentials of 300 mV and 380 mV, respectively. When used as a HER catalyst, similarly, this electrode shows excellent catalytic performance, which needs an overpotential of 90 mV to deliver 10 mA cm−2. This bifunctional electrode can allow an alkaline electrolyzer to obtain a water-splitting current density of 20 mA cm−2 at a cell voltage of around 1.66 V, which offers potential applications in the field of water splitting.

Magnet-assisted assembly of 1-dimensional hollow PtCo nanomaterials on an electrode surface

In this work, rapid and controllable confinement of one-dimensional (1D) hollow PtCo nanomaterials on an indium tin oxide (ITO) electrode surface was simply realized via magnetic attraction. The successful assembly was verified by scanning electron microscopy (SEM) and cyclic voltammetry, which showed that a longer exposure time of the electrode to the suspension of these 1D hollow nanomaterials (magnetic suspension) led to a larger amount of attached 1D hollow PtCo nanomaterials. The thus-prepared modified electrode was quite stable and displayed catalytic activity towards oxygen reduction, mainly by a four-electron process, as characterized by rotating ring-disk electrode (RRDE) experiments. Moreover, the catalytic activity can be tuned by tailoring the exposure time. This simple, rapid and controllable assembly method and excellent electrocatalytic activity of the PtCo hollow nanomaterials will make the thus-prepared modified electrode a potential candidate as an efficient and cheap cathode in low temperature fuel cells.

Coupled cobalt oxide/hollow carbon sphere as an efficient electrocatalyst for the oxygen reduction reaction

The design of a non-noble-metal electrocatalyst for the oxygen reduction reaction (ORR) is crucial for the renewable energy technologies related to electrochemical energy conversion and storage. Herein, we demonstrate a facile one-pot protocol for the highly selective growth of nanosized cobalt oxide on hollow carbon spheres. The unique structural features enable them to be an efficient non-precious catalyst for the ORR and offer potential applications in the fields of alkaline fuel cells.

Improved light-harvesting and thermal management for efficient solar-driven water evaporation using 3D photothermal cones

Solar-driven evaporation based on photothermal membrane has been proved to be promising in the field of fresh water generation, and it is considered as an emerging strategy both in laboratory and in industrial scales. However, further research efforts have to be made on light harvesting and thermal management to improve water evaporation. In this study, an extensive research was carried out to develop a bio-inspired 3D photothermal cone for high-efficiency solar-driven evaporation with minimum light reflection and heat loss to bulk water. The artificial photothermal cone with a polypyrrole (PPy) coating layer was facilely fabricated via chemical vapor deposition polymerization (CVDP). The present 3D cone with a rationally designed conical structure exhibited satisfactory absorbance around 99.2% in the entire solar spectrum, which is comparable with the performances of super-black materials. Additionally, the heat loss has been minimized by elevating the photothermal cone to narrow the contact area between water and the PPy-based cone with good wettability, thus achieving a highly efficient interface heating. The solar conversion efficiency up to 93.8% for evaporation was achieved for the photothermal cone under one sun illumination, which is about 1.7 times as high as the result obtained for a plane film. Based on our results, controlling the 3D morphology can be considered as an important strategy for designing a novel high-efficiency photothermal membrane and also, it provides new opportunities in practical application.

A hybrid composite catalyst of Fe3O4 nanoparticles-based carbon for electrochemical reduction of oxygen

The design of efficient and cheap electrocatalysts for the oxygen reduction reaction (ORR) plays a key role for renewable energy technologies such as fuel cells and metal–air batteries. Using a simple and effective route, electronically conductive acetylene black (AB) was deliberately introduced into Fe3O4/HCS-600 with enough ORR active sites to be used as an ORR catalyst. The good homogenization of the electron conductor AB and the high intimate contact of Fe3O4/HCS-600 and AB in the composite catalyst provide the possibility of facile electron accessibility. The resulting composite catalyst exhibited a high and stable electrocatalytic activity for the ORR, which is better than Fe3O4/HCS-600 or AB alone. These features may offer potential for the development of efficient ORR catalysts with low cost for alkaline fuel cells.