Lisi Xie

High-Performance Electrolytic Oxygen Evolution in Neutral Media Catalyzed by a Cobalt Phosphate Nanoarray

The topotactic conversion of cobalt phosphide nanoarray on Ti mesh into a cobalt phosphate nanoarray (Co-Pi NA) via oxidative polarization in phosphate-buffered water is presented. As a 3D oxygen evolution reaction (OER) catalyst electrode at neutral pH, the resulting Co-Pi NA/Ti shows exceptionally high catalytic activity and demands an overpotential of only 450 mV to drive a geometrical catalytic current density of 10 mA cm-2 . Notably, this catalyst also shows superior long-term electrochemical stability. The excellent catalytic activity can be attributed to that such 3D nanoarray configuration allows for the exposure of more active sites and the easier diffusion of electrolytes and oxygen.

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.

Cu(OH)2@CoCO3(OH)2·nH2O Core–Shell Heterostructure Nanowire Array: An Efficient 3D Anodic Catalyst for Oxygen Evolution and Methanol Electrooxidation

A Cu(OH)2 @CoCO3 (OH)2 ·nH2 O (CCHH) core-shell heterostructure nanowire array acts as robust 3D oxygen evolution reaction catalyst. It needs an overpotential of 270 mV to drive 50 mA cm-2 in 1.0 m KOH, outperforming CCHH nanowire arrays on copper foam and most reported Co-based oxygen evolution reaction catalysts in alkaline media. It is also efficient for methanol electrooxidation.

In Situ Derived CoB Nanoarray: A High‐Efficiency and Durable 3D Bifunctional Electrocatalyst for Overall Alkaline Water Splitting

The development of efficient bifunctional catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of extreme importance for future renewable energy systems. This Communication reports the recent finding that room-temperature treatment of CoO nanowire array on Ti mesh by NaBH4 in alkaline media leads to in situ development of CoB nanoparticles on nanowire surface. The resulting self-supported CoB@CoO nanoarray behaves as a 3D bifunctional electrocatalyst with high activity and durability for both HER (<17% current density degradation after 20 h electrolysis) and OER (<14% current density degradation after 20 h electrolysis) with the need of the overpotentials of 102 and 290 mV to drive 50 mA cm-2 in 1.0 m KOH, respectively. Moreover, its two-electrode alkaline water electrolyzer also shows remarkably high durability and only demands a cell voltage of 1.67 V to deliver 50 mA cm-2 water-splitting current with a current density retention of 81% after 20 h electrolysis. This work provides a promising methodology for the designing and fabricating of metal-boride based nanoarray as a high-active water-splitting catalyst electrode for applications.

Highly efficient electrochemical hydrogen evolution based on nickel diselenide nanowall film.

In this letter, we report on hydrothermal growth of nickel diselenide nanowall film on carbon cloth (NiSe2 NW/CC) through topotactic transformation from a Ni(OH)2 precursor based on anion exchange reactions. When tested as an integrated 3D hydrogen-evolving cathode in strongly acidic media, NiSe2 NW/CC exhibits outstanding catalytic activity superior to its powder counterpart and strong long-term durability. It displays 10 and 100 mA cm(-2) at overpotentials of 145 and 183 mV, respectively, with its catalytic activity being retained for 40 h.

A Ni2P nanosheet array integrated on 3D Ni foam: an efficient, robust and reusable monolithic catalyst for the hydrolytic dehydrogenation of ammonia borane toward on-demand hydrogen generation

Ammonia borane (AB) has been considered as one of the most attractive candidates for chemical hydrogen-storage materials; it is highly desirable but still remains a huge challenge to design and develop highly active robust non-noble-metal catalysts for on-demand hydrogen generation from AB. In this work, we demonstrate that a Ni2P nanosheet array integrated on 3D Ni foam is highly active and robust for the hydrolytic dehydrogenation of AB. This monolithic catalyst behaves as an on/off switch for on-demand hydrogen generation with a large initial turnover frequency of 42.3 mol(H2) mol(Ni2P)−1  min−1 and a lower activation energy of 44.0 kJ mol−1 under ambient conditions, outperforming all reported Ni-based noble-metal-free catalysts and some noble-metal catalysts.

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.

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.

Co-based nanowire films as complementary hydrogen- and oxygen-evolving electrocatalysts in neutral electrolyte

Designing and developing non-noble-metal electrocatalysts for efficient full water splitting at neutral pH is highly desired but still remains a huge challenge. In this communication, we report the development of homologous Co-based nanowire films, Co2N nanowire film on a Ti mesh (Co2N/TM) and Co-phosphate nanowire film on a Ti mesh (Co–Pi/TM), as complementary catalysts for stable electrochemical hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in neutral electrolyte. Co2N/TM shows remarkable HER activity with the need of an overpotential of 290 mV to drive 10 mA cm−2 in 1.0 M phosphate-buffered saline (PBS), and Co–Pi/TM is superior in OER activity affording 10 mA cm−2 at overpotentials of only 430 and 300 mV in 0.1 and 1.0 M PBS, respectively. The two-electrode water electrolyzer using Co2N/TM as a cathode and Co–Pi/TM as an anode affords a water-splitting current density of 10 mA cm−2 at a cell voltage of 1.78 V with 100% Faradaic efficiency in 1.0 M PBS, promising the practical uses of such homologous Co-based catalyst materials in technological devices.

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.