Jian Bao

Controllable Synthesis of Ultrathin NiCo2O4 Nanosheets Incorporated onto Composite Nanotubes for Efficient Oxygen Reduction

Exploring non-precious-metal-based oxygen reduction reaction (ORR) electrocatalysts featuring high efficiency, low cost, and environmental friendliness is of great importance for the broad applications of fuel cells and metal-air batteries. In this work, ultrathin NiCo2 O4 nanosheets deposited on 1D SnO2 nanotubes (SNT) were successfully fabricated through a productive electrospinning technique followed by a sintering and low-temperature coprecipitation strategy. This hierarchically engineered architecture has ultrathin NiCo2 O4 nanosheets uniformly and fully erected on both walls of tubular SNTs, which results in improved electrochemical activity as an ORR catalyst, in terms of positive onset potential and high current density, as well as superior tolerance to crossover effects and long-term durability with respect to the commercial Pt/C catalyst. The excellent performance of SNT@NiCo2 O4 composites may originate from their rationally designed hierarchical tubular nanostructure with completely exposed active sites and interconnected 1D networks for efficient electron and electrolyte transfer; this makes these composite nanotubes promising candidates to replace platinum-based catalysts for practical fuel cell and metal-air battery applications.

Exploitation of a photoelectrochemical sensing platform for catechol quantitative determination using BiPO4 nanocrystals/BiOI heterojunction

A photoelectrochemical catechol sensor using BiPO4 nanocrystals/BiOI (BiPO4/BiOI) heterojunction is developed. BiPO4/BiOI heterojunction is fabricated via a simple one-step solvothermal method with KI and ionic liquid 1-octyl-3-methylimidazolium dihydrogen phosphate ([Omim]H2PO4). An enhanced photoelectrochemical separation efficiency is obtained due to the synergistic effect between the formation of BiPO4/BiOI heterojunction and shortening the transmission path of the electron to the surface caused by BiPO4 nanocrystals. Owing to the outstanding photoelectrochemical response of BiPO4/BiOI heterojunction to catechol, a photoelectrochemical sensor is constructed for monitoring catechol. The proposed sensor possesses reliable stability, anti-interference ability and a low detection limit with 2 ng mL-1. The linear range is from 6 to 1.20 × 104 ng mL-1. Notably, this work not only supplies a facile method for BiPO4 nanocrystals based binary heterojunction, but also helps to understand the relationship between BiPO4 nanocrystals and photoelectrochemical performance of binary heterojunction. Convincingly, this strategy can be extended to other BiPO4 nanocrystals based heterojunction and photoelectrochemical sensor platform associated with photoactive materials.

NiMoO4 nanorod deposited carbon sponges with ant-nest-like interior channels for high-performance pseudocapacitors

The mounting challenges of global energy shortage and climate change call for the development of low-cost and high performance energy storage systems. Here, we propose the facile preparation of a 3D sponge electrode material by the uniform deposition of NiMoO4 nanorods on a carbonized melamine sponge (CMS) during a solvothermal reaction. Under the templating of a macroporous CMS backbone, the obtained 3D hierarchical NiMoO4/CMS composite sponge can offer numerous electrochemical sites for faradaic redox reactions and also provide interconnected conducting carbon networks for direct and rapid charge transfer. Particularly, the unique ant-nest-like interior channels in the NiMoO4/CMS composite sponge can ensure fast ion transportation and also buffer the volume change of NiMoO4 during the long-term cycling. Benefiting from these advantages, the NiMoO4/CMS composite electrode exhibits a high specific capacitance of 1689 F g−1 at 1 A g−1, which outperforms most of the previously reported NiMoO4-based electrodes. Moreover, the asymmetric supercapacitor device fabricated utilizing the composite sponge as a binder-free positive electrode also delivers a superior cycling stability (91.9% capacity retention after 2500 cycles) and a high energy density of 48.8 W h kg−1 at a power density of 800 W kg−1. Hence, the current study provides a new protocol for the low-cost fabrication of 3D sponge-like electrodes towards practical supercapacitor applications.

The CoMo-LDH ultrathin nanosheet as a highly active and bifunctional electrocatalyst for overall water splitting

The development of inexpensive and bifunctional electrocatalysts based on earth-abundant elements for electrocatalytic water splitting, including the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is of great significance. Herein, a new type of CoMo-LDH ultrathin nanosheet was synthesized as a bifunctional electrocatalyst with both OER and HER activity for full water splitting. Benefiting from the ultrathin structure and the tuned electronic structure by the doping of Mo6+, the catalyst exhibits superior OER performance with an overpotential of 290 mV to deliver a current density of 10 mA cm−2. When acting as a HER catalyst, the catalyst shows a low overpotential of 115 mV achieving a current density of 10 mA cm−2. Furthermore, the catalyst also shows bifunctional catalytic activity with a voltage of 1.63 V at 10 mA cm−2 and exhibits excellent stability for 30 h when used in the full water splitting cell. Thus, the novel CoMo-LDH ultrathin nanosheet provides a guideline for the future design of highly active and bifunctional materials for water splitting.

Hierarchical FeCo2S4 Nanotube Arrays Deposited on 3D Carbon Foam as Binder-free Electrodes for High-performance Asymmetric Pseudocapacitors

The ever-increasing global demand for green energy resources calls for more research attention on the development of cheap and efficient energy storage systems. Herein, we propose the rational design of a 3D carbon foam electrode deposited with perpendicularly oriented FeCo2 S4 nanotubes arrays (FeCo2 S4 /CMF) for high-performance asymmetric supercapacitors. In this work, the macroporous CMF served as conducting backbone not only to enhance the electrical conductivity of the composite, but also to promote the uniform growth of FeCo2 S4 nanotubes. Deposited hierarchical FeCo2 S4 nanotubes arrays with open hollow structures can afford numerous exposed electroactive sites for Faradaic redox reaction and provide short interior channels for fast electrolyte transmission. Due to these unique features, obtained 3D hierarchical FeCo2 S4 /CMF composite foam exhibits a high specific capacitance of 2430 F g-1 (specific capacity of 337.5 mAh g-1 ) at 1 A g-1 , and excellent capacitance retention of 91 % after 5000 cycles at a high current density of 9 A g-1 , which is superior to most of those previously reported binary metal sulfide-based electrodes. Moreover, asymmetric supercapacitor device assembled using the FeCo2 S4 /CMF as positive electrode also delivers a high energy density of 78.7 W h kg-1 at a power density of 800.3 W kg-1 . Therefore, this work provides a new strategy for the low-cost synthesis of 3D foam electrodes towards high-performance supercapacitor devices.