Zhiang Liu

A porous Ni3N nanosheet array as a high-performance non-noble-metal catalyst for urea-assisted electrochemical hydrogen production

Developing highly efficient and non-noble-metal catalysts is of great importance for electrochemical energy storage and conversion. In this communication, we report the development of a porous Ni3N nanosheet array on carbon cloth (Ni3N NA/CC) as a high-performance and durable electrocatalyst for urea oxidation. To drive 10 mA cm−2, this Ni3N NA/CC only demands a potential of 1.35 V in 1.0 M KOH with 0.33 M urea. The high catalytic activity of the hydrogen evolution reaction enables Ni3N NA/CC as a bifunctional catalyst electrode for electrochemical hydrogen production and the two-electrode electrolyzer is capable of offering 10 mA cm−2 at a cell voltage of only 1.44 V, 120 mV less than that for the urea-free counterpart.

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.

Co(OH)2 Nanoparticle‐Encapsulating Conductive Nanowires Array: Room‐Temperature Electrochemical Preparation for High‐Performance Water Oxidation Electrocatalysis

It is highly desired but still remains challenging to design and develop a Co-based nanoparticle-encapsulated conductive nanoarray at room temperature for high-performance water oxidation electrocatalysis. Here, it is reported that room-temperature anodization of a Co(TCNQ)2 (TCNQ = tetracyanoquinodimethane) nanowire array on copper foam at alkaline pH leads to in situ electrochemcial oxidation of TCNQ- into water-insoluable TCNQ nanoarray embedding Co(OH)2 nanoparticles. Such Co(OH)2 -TCNQ/CF shows superior catalytic activity for water oxidation and demands only a low overpotential of 276 mV to drive a geometrical current density of 25 mA cm-2 in 1.0 m KOH. Notably, it also demonstrates strong long-term electrochemical durability with its activity being retrained for at least 25 h, a high turnover frequency of 0.97 s-1 at an overpotential of 450 mV and 100% Faradic efficiency. This study provides an exciting new method for the rational design and development of a conductive TCNQ-based nanoarray as an interesting 3D material for advanced electrochemical applications.

Homologous Catalysts Based on Fe-Doped CoP Nanoarray toward High-Performance Full Water Splitting under Benign Conditions

The design and development of earth-abundant electrocatalysts for efficient full water splitting under mild conditions are highly desired, yet remain a challenging task. A homologous Fe-doped Co-based nanoarray incorporating complementary catalysts is shown to effect high-performance and durable water splitting in near-neutral media. Iron-doped cobalt phosphate borate nanoarray on carbon cloth (Fe-Co-Pi-Bi/CC) derived from iron-doped cobalt phosphide on CC (Fe-CoP/CC) through oxidative polarization behaves as a highly active bimetallic electrocatalyst for water oxidation with an overpotential of 382 mV to afford a catalytic current density of 10 mA cm-2 in 0.1 m potassium borate (K-Bi, pH 9.2). Fe-CoP/CC is also highly active for the hydrogen evolution reaction, capable of driving 10 mA cm-2 at an overpotential of only 175 mV in 0.1 m K-Bi. A two-electrode water electrolyzer incorporating Fe-Co-Pi-Bi/CC as anode and Fe-CoP/CC as cathode achieves 10 mA cm-2 water-splitting current at a cell voltage of 1.95 V with strong long-term electrochemical durability.

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.

Se doping: an effective strategy toward Fe2O3 nanorod arrays for greatly enhanced solar water oxidation

In this communication, we first report a fast and low-temperature preparation of Se doped Fe2O3 (Se-Fe2O3) nanorod arrays grown on a Ti plate with superior photoelectrochemical (PEC) performance for water oxidation. The Se-Fe2O3 offers a photocurrent density of 1.44 mA cm−2 at 1.23 V vs. the RHE in 1.0 M NaOH under simulated light (AM 1.5 G, 100 mW cm−2) irradiation, 3.13 times that of undoped Fe2O3, with a 90 mV cathodic shift of the onset potential. Experimental studies indicate that the superior PEC activity is ascribed to the increased electrical conductivity and carrier density arising from Se doping, which is of great benefit to improve the charge separation efficiency in bulk Se-Fe2O3. The present Se-doping offers an attractive approach to fabricate high-performance semiconductor photoanodes 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.

A self-supported NiMoS4 nanoarray as an efficient 3D cathode for the alkaline hydrogen evolution reaction

Developing non-noble-metal hydrogen evolution reaction electrocatalysts with high activity is critical for future renewable energy systems. Here we describe the development of a self-supported NiMoS4 nanosheet array on Ti mesh (NiMoS4/Ti) through a facile two-step hydrothermal strategy. As a 3D nanoarray electrode for electrochemical hydrogen evolution, NiMoS4/Ti shows exceptionally high catalytic activity and strong durability in 0.1 M KOH (pH: 13). It needs overpotentials of only 194 and 263 mV to drive geometrical catalytic current densities of 10 and 50 mA cm−2, respectively. Moreover, such a catalyst also demonstrates superior long-term stability with a high turnover frequency of 0.75 mol H2 s−1 at an overpotential of 148 mV. Density functional theory calculations suggest a more favorable hydrogen adsorption free energy on the NiMoS4 surface.

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.

Highly efficient and durable water oxidation in a near-neutral carbonate electrolyte electrocatalyzed by a core–shell structured NiO@Ni–Ci nanosheet array

The development of cost-effective and high-performance water oxidation electrocatalysts operating in carbonate (Ci) electrolytes is highly desired but still remains a great challenge. In this communication, we report the in situ electrochemical development of an amorphous Ni–Ci layer on a NiO nanosheet array supported on carbon cloth (NiO@Ni–Ci/CC) as a 3D catalyst electrode for water oxidation in 1.0 M KHCO3 (pH: 8.3). To drive a geometrical catalytic current density of 15 mA cm−2, such core–shell structured NiO@Ni–Ci/CC only demands an overpotential of 387 mV, with its catalytic activity being maintained for at least 25 h. And at an overpotential of 500 mV, this catalyst electrode achieves a high turnover frequency of 0.18 mol O2 per s.