Ningyan Cheng

NiSe Nanowire Film Supported on Nickel Foam: An Efficient and Stable 3D Bifunctional Electrode for Full Water Splitting.

Active and stable electrocatalysts made from earth-abundant elements are key to water splitting for hydrogen production through electrolysis. The growth of NiSe nanowire film on nickel foam (NiSe/NF) in situ by hydrothermal treatment of NF using NaHSe as Se source is presented. When used as a 3D oxygen evolution electrode, the NiSe/NF exhibits high activity with an overpotential of 270 mV required to achieve 20 mA cm(-2) and strong durability in 1.0 M KOH, and the NiOOH species formed at the NiSe surface serves as the actual catalytic site. The system is also highly efficient for catalyzing the hydrogen evolution reaction in basic media. This bifunctional electrode enables a high-performance alkaline water electrolyzer with 10 mA cm(-2) at a cell voltage of 1.63 V.

Carbon Nanotubes Decorated with CoP Nanocrystals: A Highly Active Non-Noble-Metal Nanohybrid Electrocatalyst for Hydrogen Evolution†

The development of effective and inexpensive hydrogen evolution reaction (HER) electrocatalysts for future renewable energy systems is highly desired. The strongly acidic conditions in proton exchange membranes create a need for acid-stable HER catalysts. A nanohybrid that consists of carbon nanotubes decorated with CoP nanocrystals (CoP/CNT) was prepared by the low-temperature phosphidation of a Co3O4/CNT precursor. As a novel non-noble-metal HER catalyst operating in acidic electrolytes, the nanohybrid exhibits an onset overpotential of as low as 40 mV, a Tafel slope of 54 mV dec(-1), an exchange current density of 0.13 mA cm(-2), and a Faradaic efficiency of nearly 100 %. This catalyst maintains its catalytic activity for at least 18 hours and only requires overpotentials of 70 and 122 mV to attain current densities of 2 and 10 mA cm(-2), respectively.

Self-Supported Cu3P Nanowire Arrays as an Integrated High-Performance Three-Dimensional Cathode for Generating Hydrogen from Water†

Searching for inexpensive hydrogen evolution reaction (HER) electrocatalysts with high activity has attracted considerable research interest in the past years. Reported herein is the topotactic fabrication of self-supported Cu3 P nanowire arrays on commercial porous copper foam (Cu3 P NW/CF) from its Cu(OH)2 NW/CF precursor by a low-temperature phosphidation reaction. Remarkably, as an integrated three-dimensional hydrogen-evolving cathode operating in acidic electrolytes, Cu3 P NW/CF maintains its activity for at least 25 hours and exhibits an onset overpotential of 62 mV, a Tafel slope of 67 mV dec(-1) , and a Faradaic efficiency close to 100 %. Catalytic current density can approach 10 mA cm(-2) at an overpotential of 143 mV.

Au-Nanoparticle-Loaded Graphitic Carbon Nitride Nanosheets: Green Photocatalytic Synthesis and Application toward the Degradation of Organic Pollutants

Au nanoparticles (AuNPs) were loaded on graphitic carbon nitride (g-C3N4) nanosheets prepared by ultrasonication-assisted liquid exfoliation of bulk g-C3N4 via green photoreduction of Au(III) under visible light irradiation using g-C3N4 as an effective photocatalyst. The nanohybrids show superior photocatalytic activities for the decomposition of methyl orange under visible-light irradiation to bulk g-C3N4, g-C3N4 nanosheets, and AuNP/bulk g-C3N4 hybrids.

Cobalt Phosphide Nanowires: Efficient Nanostructures for Fluorescence Sensing of Biomolecules and Photocatalytic Evolution of Dihydrogen from Water under Visible Light

The detection of specific DNA sequences plays an important role in the identification of disease-causing pathogens and genetic diseases, and photochemical water splitting offers a promising avenue to sustainable, environmentally friendly hydrogen production. Cobalt-phosphorus nanowires (CoP NWs) show a high fluorescence quenching ability and different affinity toward single- versus double-stranded DNA. Based on this result, the utilization of CoP NWs as fluorescent DNA nanosensors with a detection limit of 100 pM and a selectivity down to single-base mismatch was demonstrated. The use of a thrombin-specific DNA aptamer also enabled the selective detection of thrombin. The photoinduced electron transfer from the excited dye that labels the oligonucleotide probe to the CoP semiconductor led to efficient fluorescence quenching, and largely enhanced the photocatalytic evolution of hydrogen from water under visible light.

Self-supported NiMo hollow nanorod array: an efficient 3D bifunctional catalytic electrode for overall water splitting

Large-scale industrial application of electrochemical water splitting calls for remarkable non-noble metal electrocatalysts. Herein, we report on the synthesis of a NiMo-alloy hollow nanorod array supported on Ti mesh (NiMo HNRs/TiM) using a template-assisted electrodeposition method. The NiMo HNRs/TiM behaves as a durable efficient oxygen evolution anode with 10 mA cm−2 at an overpotential of 310 mV in 1.0 M KOH. Coupled with its superior catalytic performance for hydrogen evolution with 10 mA cm−2 at an overpotential of 92 mV, we made an alkaline electrolyzer using this bifunctional electrode with 10 mA cm−2 at a cell voltage of 1.64 V.

Template-assisted synthesis of CoP nanotubes to efficiently catalyze hydrogen-evolving reaction

For the first time, we demonstrate a template-assisting synthesis to make CoP nanotubes (CoP NTs) through low-temperature phosphidation of Co salt inside a porous anodic aluminium oxide template followed by dilute HF etching. Such CoP NTs exhibit excellent hydrogen-evolution catalytic activity and durability in an acidic medium, which is superior to their nanoparticle counterparts, with a Faradaic yield of nearly 100%. The fundamental insight for the catalytic enhancement mechanism is also explored.

A Fe-doped Ni3S2 particle film as a high-efficiency robust oxygen evolution electrode with very high current density

The efficiency of water splitting is mainly limited by the low rate of the oxygen evolution reaction (OER) and it is thus of great importance but still remains a huge challenge to develop efficient OER catalysts capable of delivering high current densities at low overpotentials. Herein, we describe our recent finding that a Fedoped Ni3S2 particle film with 11.8% Fe-content hydrothermally grown on nickel foam (Fe-11.8%-Ni3S2/NF) behaves as a highly active robust oxygen evolution electrode in strongly alkaline media. This electrode needs an overpotential of only 253 mV to achieve 100 mA cm(-2) with a Tafel slope of 65.5 mV dec(-1) and maintains its catalytic activity for at least 14 h in 1 M KOH, and the NiOOH and FeOOH formed at the Fe-11.8%-Ni3S2 surface are the actual catalytic sites. Notably, it also operates efficiently and stably in 30 wt% KOH, capable of affording very high current densities of 500 and 1000 mA cm(-2) at small overpotentials of 238 and 269 mV, respectively, with a faradaic efficiency of 100%.