Fengyu Xie

High‐Performance Non‐Enzyme Hydrogen Peroxide Detection in Neutral Solution: Using a Nickel Borate Nanoarray as a 3D Electrochemical Sensor

It is highly attractive to construct natural enzyme-free nanoarray architecture as a 3D catalyst for hydrogen peroxide detection due to its great specific surface area and easy accessibility to target molecules. In this communication, we demonstrate that nickel borate nanoarray supported on carbon cloth (Ni-Bi/CC) behaves as an efficient catalyst electrode for H2 O2 electro-reduction in neutral media. As a non-enzymatic electrochemical H2 O2 sensor, such Ni-Bi/CC shows superior sensing performances with a fast response time (less than 3 s), a low detection limit (0.85 nm, S/N=3), and a high sensitivity (18320 μA mm cm-2 ). Importantly, it also demonstrates favourable reproducibility and long-term stability.

MoO3 nanosheets for efficient electrocatalytic N2 fixation to NH3

The synthesis of NH3 heavily depends on the energy-intensive Haber–Bosch process with a large amount of greenhouse gas emission. Electrochemical reduction offers a carbon-neutral process to convert N2 to NH3 at ambient conditions, but requires efficient and stable catalysts for the N2 reduction reaction. Mo-dependent nitrogenases and synthetic molecular complexes have attracted increasing attention for N2 fixation; however, less attention has been paid to Mo-based nanocatalysts for electrochemical N2 conversion to NH3. Herein, we report that MoO3 nanosheets act as an efficient non-noble-metal catalyst for electrochemical N2 fixation to NH3 with excellent selectivity at room temperature and atmospheric pressure. In 0.1 M HCl, this catalyst exhibits remarkable NRR activity with an NH3 yield of 4.80 × 10−10 mol s−1 cm−2 (29.43 μg h−1 mgcat.−1) and a faradaic efficiency of 1.9%. Moreover, this catalyst also shows high electrochemical stability and durability. Density functional theory calculations reveal that the outermost Mo atoms serve as the active sites for effective N2 adsorption.

Remarkable enhancement of the alkaline oxygen evolution reaction activity of NiCo2O4 by an amorphous borate shell

It is highly desirable but still a challenging task to find a simple, fast and straightforward method to greatly improve the alkaline oxygen evolution reaction (OER) performance of a NiCo2O4 catalyst. In this communication, we demonstrate that developing an amorphous borate shell on a NiCo2O4 surface can boost its OER activity in alkaline media. As a 3D catalyst electrode, a NiCo2O4@Ni–Co–B nanoarray on carbon cloth needs an overpotential of only 270 mV to achieve a geometrical catalytic current density of 10 mA cm−2 in 1.0 M KOH, which is 100 mV less than that for a NiCo2O4 nanoarray. Notably, this electrode also demonstrates strong electrochemical durability, maintaining its activity for at least 100 h. The superior activity of NiCo2O4@Ni–Co–B is attributed to the amorphous Ni–Co–B shell on NiCo2O4 favoring the in situ electrochemical generation of more active species during water oxidation.

Facilitating Active Species Generation by Amorphous NiFe-Bi Layer Formation on NiFe-LDH Nanoarray for Efficient Electrocatalytic Oxygen Evolution at Alkaline pH

Searching for a simple and fast strategy to effectively enhance the oxygen evolution reaction (OER) performance of non-noble-metal electrocatalysts in alkaline media remains a significant challenge. Herein, the OER activity of NiFe-LDH nanoarray on carbon cloth (NiFe-LDH/CC) in alkaline media is shown to be greatly boosted by an amorphous NiFe-Borate (NiFe-Bi ) layer formation on NiFe-layered double hydroxide (NiFe-LDH) surface. Such a NiFe-LDH@NiFe-Bi /CC catalyst electrode only needs an overpotential of 294 mV to drive 50 mA cm-2 in 1.0 m KOH; 116 mV less than that needed by NiFe-LDH/CC. Notably, this electrode also demonstrates strong long-term electrochemical durability. The superior activity is ascribed to the pre-formed amorphous NiFe-Bi layer effectively promoting active species generation on the NiFe-LDH surface. This work opens up exciting new avenues for developing high-performance water-oxidation catalyst materials for application.

Self‐Templating Construction of Hollow Amorphous CoMoS4 Nanotube Array towards Efficient Hydrogen Evolution Electrocatalysis at Neutral pH

Environmentally friendly electrochemical hydrogen production needs the development of earth-abundant catalyst materials for the hydrogen evolution reaction with high activity and durability at neutral pH. In this work, the self-templating construction of a hollow amorphous CoMoS4 nanotube array on carbon cloth (CoMoS4 NTA/CC) is reported, using hydrothermal treatment of a Co(OH)F nanowire array on CC in (NH4 )2 MoS4 solution. When used as a 3D electrode for hydrogen evolution electrocatalysis, the resulting CoMoS4 NTA/CC demonstrates superior catalytic activity and strong long-term electrochemical durability in 1.0 M phosphate buffer solution (pH=7). It shows small onset overpotential of 21 mV and requires low overpotentials of 104 and 179 mV to drive geometrical current densities of 10 and 50 mA cm-2 , respectively. Density functional theory calculations suggest that CoMoS4 has a more favorable hydrogen adsorption free energy than Co(OH)F.

Rational design of a multidimensional N-doped porous carbon/MoS2/CNT nano-architecture hybrid for high performance lithium–sulfur batteries

Exploring a stable and high-efficiency sulfur cathode with strong polarity and a robust porous conductive framework is a critical challenge to develop advanced lithium–sulfur (Li–S) batteries. Herein, a multidimensional N-doped porous carbon/MoS2/CNT (FSC/MoS2/CNT) nano-architecture hybrid is rationally designed and successfully fabricated by the facile pyrolysis and hydrothermal processes. For the nano-architecture composite, the porous carbon embedded with electroconductive acid-treated CNTs effectively enhances the flexibility and constructs a conductive network for rapid ion/electron transfer; specifically, a synergistic action of polar MoS2 and electronegative doped N atoms significantly strengthens the chemical affinity with polysulfides; furthermore, MoS2 exhibits a strong catalytic effect that can improve the redox kinetics of polysulfides. On account of the merits mentioned above, the as-built N-doped porous carbon/MoS2/CNTs@S (FSC/MoS2/CNTs@S) composite, utilized as the Li–S battery cathode, delivers a high discharge capacity of 1313.4 mA h g−1 at 0.1C, glorious rate performance with 671.6 mA h g−1 at 2.0C and remarkable cycling stability with a capacity fading rate of 0.059% per cycle for 500 cycles at 1.0C. This work provides a novel and simple strategy to design a CNT decorated polar and conductive hybrid network of doped porous carbon/transition metal sulfide for application in excellent performance Li–S batteries and numerous energy storage fields.

Enabling Effective Electrocatalytic N2 Conversion to NH3 by the TiO2 Nanosheets Array under Ambient Conditions

NH3 serves as an attractive hydrogen storage medium and a renewable energy sector for a sustainable future. Electrochemical reduction is a feasible ambient reaction to convert N2 to NH3, while it needs efficient electrocatalysts for the N2 reduction reaction (NRR) to meet the challenge associated with N2 activation. In this Letter, we report on our recent experimental finding that the TiO2 nanosheets array on the Ti plate (TiO2/Ti) is effective for electrochemical N2 conversion to NH3 at ambient conditions. When tested in 0.1 M Na2SO4, such TiO2/Ti attains a high NH3 yield of 9.16 × 10-11 mol s-1·cm-2 with corresponding Faradaic efficiency of 2.50% at -0.7 V vs reversible hydrogen electrode, outperforming most reported aqueous-based NRR electrocatalysts. It also shows excellent selectivity for NH3 formation with high electrochemical stability. The superior NRR activity is due to the enhanced adsorption and activation of N2 by oxygen vacancies in situ generated during electrochemical tests.