Ruixiang Ge

Cobalt–borate nanowire array as a high-performance catalyst for oxygen evolution reaction in near-neutral media

The development of an efficient catalyst for electrolytic water oxidation under neutral or near-neutral environment remains a great challenge. In this communication, we developed a high-performance cobalt–borate nanowire array on a Ti mesh (Co–Bi NA/Ti) from a CoSe2 nanowire array via rapid topotactic conversion. As a three-dimensional water oxidation electrode, such Co–Bi NA/Ti, demands only 420 mV to drive a geometrical catalytic current density of 10 mA cm−2. It exhibits superior activity when compared to most of the reported non-precious metal catalysts working under benign conditions. In addition, Co–Bi NA/Ti also displays good stability and high turnover frequency (0.59 s−1 at an overpotential of 600 mV) in 0.1 M potassium borate (pH: 9.2). This novel research finding has paved a new path for developing highly active oxygen evolution reaction electrocatalysts in near-neutral media.

In situ formation of a 3D core/shell structured Ni3N@Ni–Bi nanosheet array: an efficient non-noble-metal bifunctional electrocatalyst toward full water splitting under near-neutral conditions

It is of great importance but still remains a key challenge to develop non-noble-metal bifunctional catalysts for efficient full water splitting under mild pH conditions. In this communication, we report the in situ electrochemical development of an ultrathin Ni–Bi layer on a metallic Ni3N nanosheet array supported on a Ti mesh (Ni3N@Ni–Bi NS/Ti) as a durable 3D core/shell structured nanoarray electrocatalyst for water oxidation at near-neutral pH. The Ni3N@Ni–Bi NS/Ti demands overpotentials of 405 and 382 mV to deliver a geometrical catalytic current density of 10 mA cm−2 in 0.1 and 0.5 M K–Bi (pH: 9.2), respectively, superior in activity to Ni3N NS/Ti and most reported non-precious metal catalysts under benign conditions. It also performs efficiently for the hydrogen evolution reaction requiring an overpotential of 265 mV for 10 mA cm−2 and its two-electrode electrolyser affords 10 mA cm−2 at a cell voltage of 1.95 V in 0.5 M K–Bi at 25 °C.

In situ surface derivation of an Fe–Co–Bi layer on an Fe-doped Co3O4 nanoarray for efficient water oxidation electrocatalysis under near-neutral conditions

Developing high-performance water oxidation electrocatalysts working under mild conditions is highly desirable, but still remains challenging. In this communication, we report the in situ surface derivation of an Fe–Co–Bi layer (4–7 nm in thickness) on an Fe-doped Co3O4 nanowire array supported on carbon cloth (Fe–Co3O4/CC). As a 3D catalyst electrode for water oxidation, such a core–shell Fe–Co3O4@Fe–Co–Bi nanoarray (Fe–Co3O4@Fe–Co–Bi/CC) demonstrates superior activity over that of a Co3O4-derived nanoarray catalyst, with the need of an overpotential of 420 mV to drive a geometrical catalytic current density of 10 mA cm−2 in 0.1 M potassium borate (pH = 9.2). Notably, this catalyst also shows good long-term stability with high turnover frequencies.

A Ni(OH)2–PtO2 hybrid nanosheet array with ultralow Pt loading toward efficient and durable alkaline hydrogen evolution

The design and development of highly active electrocatalysts for the hydrogen evolution reaction (HER) in alkaline media is of significant importance. In this communication, we report the direct growth of an ultralow-Pt-content (Pt content: 5.1 wt%) Ni(OH)2–PtO2 hybrid nanosheet array on a Ti mesh (Ni(OH)2–PtO2 NS/Ti), carried out by hydrothermal treatment of a Ni(OH)2 nanosheet array on a Ti mesh (Ni(OH)2 NS/Ti) in the presence of [PtCl6]2−. When used as a 3D catalyst electrode for the HER, the resulting Ni(OH)2–PtO2 NS/Ti exhibits superior activity with the need of an overpotential of only 31.4 mV to deliver a geometrical catalytic current density of 4 mA cm−2 in 0.1 M KOH. Remarkably, this catalyst also shows strong long-term electrochemical durability for at least 100 h with a faradaic efficiency close to 100%. Density functional theory calculations reveal that the Ni(OH)2/PtO2 interface can promote the kinetics of H2O dissociation and tune the hydrogen adsorption free energy to a more moderate value, thereby promoting the HER.

Three-Dimensional Nickel–Borate Nanosheets Array for Efficient Oxygen Evolution at Near-Neutral pH

Nickel-borate nanosheets array on titanium mesh (Ni-Bi NA/TM) was derived from NiSe2 nanosheets array on titanium mesh (NiSe2 NA/TM) by electrochemical transformation. As a three-dimensional electrode, Ni-Bi NA/TM exhibited high catalytic activity toward the oxygen evolution reaction and required a low overpotential of 430 mV at 10 mA cm-2 in 0.1 m potassium borate (pH 9.2), with outstanding long-term stability and high turnover frequency.

Self-supported CoMoS4 nanosheet array as an efficient catalyst for hydrogen evolution reaction at neutral pH

Development of earth-abundant electrocatalysts, particularly for high-efficiency hydrogen evolution reaction (HER) under benign conditions, is highly desired, but still remains a serious challenge. Herein, we report a high-performance amorphous CoMoS4 nanosheet array on carbon cloth (CoMoS4 NS/CC), prepared by hydrothermal treatment of a Co(OH)F nanosheet array on a carbon cloth (Co(OH)F NS/CC) in (NH4)2MoS4 solution. As a three-dimensional HER electrode, CoMoS4 NS/CC exhibits remarkable activity in 1.0 M phosphate buffer saline (pH 7), only requiring an overpotential of 183 mV to drive a geometrical current density of 10 mA·cm–2. This overpotential is 140 mV lower than that for Co(OH)F NS/CC. Notably, this electrode also shows outstanding electrochemical durability and nearly 100% Faradaic efficiency. Density functional theory calculations suggest that CoMoS4 has a more favorable hydrogen adsorption free energy than Co(OH)F.

Topotactic Conversion of α-Fe2O3 Nanowires into FeP as a Superior Fluorosensor for Nucleic Acid Detection: Insights from Experiment and Theory

Nanostructures possess distinct quenching ability toward fluorophores with different emission frequencies and have been intensively used as nanoquenchers for homogeneous nucleic acid detection. Complete understanding of such a sensing system will provide significant guidance for the design of superior sensing materials, which is still lacking. In this Letter, we demonstrate the development of FeP nanowires as a nanoquencher for high-performance fluorescent nucleic acid detection with much superior performance to α-Fe2O3 counterparts. The whole detection process is complete within 1 min, and this fluorosensor presents a detection limit as low as 4 pM with strong discrimination of single-point mutation. Electrochemical tests and density functional theory calculations reveal that FeP NWs are superior in both conductivity for facilitated electron diffusion and hydrogen-evolving catalytic activity for favorable electron depletion, providing further experimental and theoretical insights into the enhanced sensing performance of the FeP nanosensor. Both faster electron transfer kinetics and stronger electron-consuming ability via catalyzed proton reduction enable FeP nanowires to be a superb nucleic acid nanosensor for applications.

Core–Shell NiFe-LDH@NiFe-Bi Nanoarray: In Situ Electrochemical Surface Derivation Preparation toward Efficient Water Oxidation Electrocatalysis in near-Neutral Media

The corrosion issue with acidic and alkaline water electrolyzers can be avoided by developing water oxidation catalysts performing efficiently under benign conditions. In this Letter, we report that a NiFe-borate layer can be generated on a NiFe-layered double hydroxide nanosheet array hydrothermally grown on carbon cloth via an in situ electrochemical surface derivation process in potassium borate (K-Bi) solution. The resulting 3D NiFe-LDH@NiFe-Bi nanoarray (NiFe-LDH@NiFe-Bi/CC) demonstrates high activity for water oxidation, demanding overpotentials of 444 and 363 mV to achieve 10 mA cm-2 in 0.1 and 0.5 M K-Bi (pH: 9.2), respectively, rivaling the performances of most reported non-noble-metal catalysts in near-neutral media. Notably, this electrode also shows strong electrochemical durability with a high turnover frequency of 0.54 mol O2 s-1 at overpotential of 600 mV. All these features promise its use as an efficient earth-abundant catalyst material for water oxidation under eco-friendly conditions.

Cobalt-Borate Nanoarray: An Efficient and Durable Electrocatalyst for Water Oxidation under Benign Conditions

The development of efficient earth-abundant electrocatalysts for oxygen evolution reaction (OER) under benign conditions is still urgent and challenging. Herein, we report the electrochemical generation of novel Co-Bi nanoarray on carbon cloth (Co-Bi NA/CC) from CoS2 nanoarray precursor. As a three-dimensional anode, such Co-Bi NA/CC exhibits excellent electrocatalytic performance for OER with the overpotential requirement of 411 mV to drive 10 mA cm-2. Notably, this electrode also demonstrates outstanding long-term electrochemical durability for 20 h.

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.