Jin-Xian Feng

Design of Pd/PANI/Pd Sandwich-Structured Nanotube Array Catalysts with Special Shape Effects and Synergistic Effects for Ethanol Electrooxidation

Low cost, high activity, and long-term durability are the main requirements for commercializing fuel cell electrocatalysts. Despite tremendous efforts, developing non-Pt anode electrocatalysts with high activity and long-term durability at low cost remains a significant technical challenge. Here we report a new type of hybrid Pd/PANI/Pd sandwich-structured nanotube array (SNTA) to exploit shape effects and synergistic effects of Pd-PANI composites for the oxidation of small organic molecules for direct alcohol fuel cells. These synthesized Pd/PANI/Pd SNTAs exhibit significantly improved electrocatalytic activity and durability compared with Pd NTAs and commercial Pd/C catalysts. The unique SNTAs provide fast transport and short diffusion paths for electroactive species and high utilization rate of catalysts. Besides the merits of nanotube arrays, the improved electrocatalytic activity and durability are especially attributed to the special Pd/PANI/Pd sandwich-like nanostructures, which results in electron delocalization between Pd d orbitals and PANI π-conjugated ligands and in electron transfer from Pd to PANI.

FeOOH/Co/FeOOH Hybrid Nanotube Arrays as High-Performance Electrocatalysts for the Oxygen Evolution Reaction

Herein, we developed FeOOH/Co/FeOOH hybrid nanotube arrays (HNTAs) supported on Ni foams for oxygen evolution reaction (OER). The inner Co metal cores serve as highly conductive layers to provide reliable electronic transmission, and can overcome the poor electrical conductivity of FeOOH efficiently. DFT calculations demonstrate the strong electronic interactions between Co and FeOOH in the FeOOH/Co/FeOOH HNTAs, and the hybrid structure can lower the energy barriers of intermediates and thus promote the catalytic reactions. The FeOOH/Co/FeOOH HNTAs exhibit high electrocatalytic performance for OER, such as low onset potential, small Tafel slope, and excellent long-term durability, and they are promising electrocatalysts for OER in alkaline solution.

Design and Synthesis of FeOOH/CeO2 Heterolayered Nanotube Electrocatalysts for the Oxygen Evolution Reaction

FeOOH/CeO2 heterolayered nanotubes supported on Ni foam as efficient oxygen evolution electrocatalysts are reported. The hybrid structure can obviously promote the catalytic performance for the oxygen evolution reaction, such as low onset potential, high electroactivity, and excellent long-term durability. This study provides a new route to the design and fabrication of electrocatalysts with high electroactivity and durability for oxygen evolution.

Co(OH)2@PANI Hybrid Nanosheets with 3D Networks as High‐Performance Electrocatalysts for Hydrogen Evolution Reaction

Hybrid electrocatalysts with excellent electrocatalytic activity for hydrogen reduction are fabricated using an efficient and facile electrochemical route. The electronic and synergistic effects between Co(OH)2 and polyaniline (PANI) in the composite structure are the key factors that generate the high electrocatalytic activity and excellent stability. A highly efficient, non-precious metal-based flexible electrocatalyst for high-performance electrocatalysts is shown, which reveals a novel route for the design and synthesis of electrocatalysts.

Asymmetric Paper Supercapacitor Based on Amorphous Porous Mn3O4 Negative Electrode and Ni(OH)2 Positive Electrode: A Novel and High-Performance Flexible Electrochemical Energy Storage Device

Here we synthesize novel asymmetric all-solid-state paper supercapacitors (APSCs) based on amorphous porous Mn3O4 grown on conducting paper (NGP) (Mn3O4/NGP) negative electrode and Ni(OH)2 grown on NGP (Ni(OH)2/NGP) as positive electrode, and they have attracted intensive research interest owing to their outstanding properties such as being flexible, ultrathin, and lightweight. The fabricated APSCs exhibit a high areal Csp of 3.05 F/cm3 and superior cycling stability. The novel asymmetric APSCs also exhibit high energy density of 0.35 mW h/cm3, high power density of 32.5 mW/cm3, and superior cycling performance (<17% capacitance loss after 12,000 cycles at a high scan rate of 100 mV/s). This work shows the first example of amorphous porous metal oxide/NGP electrodes for the asymmetric APSCs, and these systems hold great potential for future flexible electronic devices.

Flexible symmetrical planar supercapacitors based on multi-layered MnO2/Ni/graphite/paper electrodes with high-efficient electrochemical energy storage

High-performance planar supercapacitors have attracted increasing attention because of their thin, light and flexible abilities. Here we developed novel flexible symmetrical planar supercapacitors (FSPSCs) by using the multi-layered MnO2/Ni/graphite/paper electrodes that were fabricated by sequentially coating a graphite layer, Ni layer, and MnO2 layer on ordinary cellulose paper. The MnO2/Ni/graphite/paper electrodes show a large specific capacitance (Csp) of 175 mF cm−2 at a scan rate of 5 mV s−1. The assembled FSPSCs based on the multi-layered MnO2/Ni/graphite/paper electrodes exhibit a large volumetric Csp (1020 mF cm−3 at 5 mV s−1) and a superior long-term cycle stability (less 4% loss of the maximum Csp after 6000 cycles). The FSPSCs based on the multi-layered MnO2/Ni/graphite/paper electrodes may open up new opportunities in developing novel supercapacitor devices because of the low-cost, high performance, and facile large-scale fabrication procedures.

Efficient Hydrogen Evolution Electrocatalysis Using Cobalt Nanotubes Decorated with Titanium Dioxide Nanodots

TiO2 Co nanotubes decorated with nanodots (TiO2 NDs/Co NSNTs-CFs) are reported as high-performance earth-abundant electrocatalysts for the hydrogen evolution reaction (HER) in alkaline solution. TiO2 NDs/Co NSNTs can promote water adsorption and optimize the free energy of hydrogen adsorption. More importantly, the absorbed water can be easily activated in the presence of the TiO2 -Co hybrid structure. These advantages will significantly promote HER. TiO2 NDs/Co NSNTs-CFs as electrocatalysts show a high catalytic performance towards HER in alkaline solution. This study will open up a new avenue for designing and fabricating low-cost high-performance HER catalysts.

Efficient Hydrogen Evolution on Cu Nanodots-Decorated Ni3S2 Nanotubes by Optimizing Atomic Hydrogen Adsorption and Desorption

Low-cost transition-metal dichalcogenides (MS2) have attracted great interest as alternative catalysts for hydrogen evolution. However, a significant challenge is the formation of sulfur-hydrogen bonds on MS2 (S-Hads), which will severely suppress hydrogen evolution reaction (HER). Here we report Cu nanodots (NDs)-decorated Ni3S2 nanotubes (NTs) supported on carbon fibers (CFs) (Cu NDs/Ni3S2 NTs-CFs) as efficient electrocatalysts for HER in alkaline media. The electronic interactions between Cu and Ni3S2 result in Cu NDs that are positively charged and can promote water adsorption and activation. Meanwhile, Ni3S2 NTs are negatively charged and can weaken S-Hads bonds formed on catalyst surfaces. Therefore, the Cu/Ni3S2 hybrids can optimize H adsorption and desorption on electrocatalysts and can promote both Volmer and Heyrovsky steps of HER. The strong interactions between Cu and Ni3S2 cause the Cu NDs/Ni3S2 NTs-CFs electrocatalysts to exhibit the outstanding HER catalytic performance with low onset potential, high catalytic activity, and excellent stability.

Pt-like Hydrogen Evolution Electrocatalysis on PANI/CoP Hybrid Nanowires by Weakening the Shackles of Hydrogen Ions on the Surfaces of Catalysts

The search for high active, stable, and cost-efficient hydrogen evolution reaction (HER) electrocatalysts for water electrolysis has attracted great interest. The coordinated water molecules in the hydronium ions will obviously reduce the positive charge density of H+ and hamper the ability of H+ to receive electrons from the cathode, leading to large overpotential of HER on nonprecious metal catalysts. Here we realize Pt-like hydrogen evolution electrocatalysis on polyaniline (PANI) nanodots (NDs)-decorated CoP hybrid nanowires (HNWs) supported on carbon fibers (CFs) (PANI/CoP HNWs-CFs) as PANI can effectively capture H+ from hydronium ions to form protonated amine groups that have higher positive charge density than those of hydronium ions and can be electro-reduced easily. The PANI/CoP HNWs-CFs as low-cost electrocatalysts show excellent catalytic performance toward HER in acidic solution, such as super high catalytic activity, small Tafel slope, and superior stability.

Multi-layered Pt/Ni nanotube arrays with enhanced catalytic performance for methanol electrooxidation

Novel Pt/Ni multi-layered nanotube arrays (MLNTAs) are synthesized by template-assisted layer-by-layer electrodeposition. The unique multi-layered structures in nanotube walls provide a new method to study the effects of heterointerfaces and structures on methanol electrooxidation. For the fabricated Pt/Ni MLNTAs, especially Ni@Pt@Ni@Pt NTAs, we observed obvious enhancements in the catalytic activity and durability compared with the monometallic Pt nanotube arrays (NTAs) and many Pt-based catalysts reported in the literature studies. Our synthesis approach presents a strategy to broaden the heterointerfacial and structural effects for harnessing the true catalytic potential of Pt-based electrocatalysts and may lead to wide applications for energy conversion and storage.