Low-Voltage Electrolytic Hydrogen Production Derived from Efficient Water and Ethanol Oxidation on Fluorine-Modified FeOOH Anode

Highly active, earth-abundant anode catalysts are urgently required for the development of electrolytic devices for hydrogen generation. However, the reaction efficiencies of most developed electrocatalysts have been intrinsically limited due to their insufficient adsorption of reactants leading to high energy intermediates. Here, we establish that electronegative fluorine can moderate the binding energy between the Fe sites (FeOOH) and reactants (OH^– or C₂H₅O^–), resulting in more optimized adsorption, and can enhance the positive charge densities on the Fe sites to facilitate oxygen evolution reaction (OER) and ethanol oxidation. Consequently, a low electrolytic voltage (1.43 V to achieve 10 mA cm^–2) for H₂ production was obtained by integrating the efficiently anodic behaviors of OER and ethanol oxidation. The results reported herein point to fluorine moderation as a promising pathway for developing optimal electrocatalysts and contribute to ongoing efforts of mimicking water splitting

Self-Sacrificial Template Strategy Coupled with Smart <i>in Situ</i> Seeding for Highly Oriented Metal–Organic Framework Layers: From Films to Membranes

Self-Sacrificial Template Strategy Coupled with Smart <i>in Situ</i> Seeding for Highly Oriented Metal–Organic Framework Layers: From Films to Membrane

Design of Pd/PANI/Pd Sandwich-Structured Nanotube Array Catalysts with Special Shape Effects and Synergistic Effects for Ethanol Electrooxidation

Low cost, high activity, and long-term durability are the main requirements for commercializing fuel cell electrocatalysts. Despite tremendous efforts, developing non-Pt anode electrocatalysts with high activity and long-term durability at low cost remains a significant technical challenge. Here we report a new type of hybrid Pd/PANI/Pd sandwich-structured nanotube array (SNTA) to exploit shape effects and synergistic effects of Pd-PANI composites for the oxidation of small organic molecules for direct alcohol fuel cells. These synthesized Pd/PANI/Pd SNTAs exhibit significantly improved electrocatalytic activity and durability compared with Pd NTAs and commercial Pd/C catalysts. The unique SNTAs provide fast transport and short diffusion paths for electroactive species and high utilization rate of catalysts. Besides the merits of nanotube arrays, the improved electrocatalytic activity and durability are especially attributed to the special Pd/PANI/Pd sandwich-like nanostructures, which results in electron delocalization between Pd d orbitals and PANI π-conjugated ligands and in electron transfer from Pd to PANI

Self-Assembled Close-Packed MnO₂ Nanoparticles Anchored on a Polyethylene Separator for Lithium–Sulfur Batteries

Separator modification has been proved to be an effective approach for overcoming lithium polysulfide (LiPS) shuttling in lithium–sulfur (Li–S) cells. However, the weight and stability of the modified layer also affect the cycling properties and the energy density of Li–S cells. Here, we initially construct an ultrathin and lightweight MnO₂ layer (380 nm, 0.014 mg cm^–2) on a commercial polyethylene (PE) separator (MnO₂@PE) through a chemical self-assembly method. This MnO₂ layer is tightly anchored onto the PE substrate because of the presence of oxygen-containing groups that form a relatively strong chemical force between the MnO₂ nanoparticles and the PE substrate. In addition, the mechanical strength of the separator is not affected by this modification procedure. Moreover, because of the catalytic effect and compactness of the MnO₂ layer, the MnO₂@PE separator can greatly suppress LiPS shuttling. As a result, the application of this MnO₂@PE separator in Li–S batteries leads to high reversible capacity and superior cycling stability. This strategy provides a novel approach to separator surface modification

Design and Synthesis of MnO₂/Mn/MnO₂ Sandwich-Structured Nanotube Arrays with High Supercapacitive Performance for Electrochemical Energy Storage

We demonstrate the design and fabrication of novel nanoarchitectures of MnO₂/Mn/MnO₂ sandwich-like nanotube arrays for supercapacitors. The crystalline metal Mn layers in the MnO₂/Mn/MnO₂ sandwich-like nanotubes uniquely serve as highly conductive cores to support the redox active two-double MnO₂ shells with a highly electrolytic accessible surface area and provide reliable electrical connections to MnO₂ shells. The maximum specific capacitances of 937 F/g at a scan rate of 5 mV/s by cyclic voltammetry (CV) and 955 F/g at a current density of 1.5 A/g by chronopotentiometry were achieved for the MnO₂/Mn/MnO₂ sandwich-like nanotube arrays in solution of 1.0 M Na₂SO₄. The hybrid MnO₂/Mn/MnO₂ sandwich-like nanotube arrays exhibited an excellent rate capability with a high specific energy of 45 Wh/kg and specific power of 23 kW/kg and excellent long-term cycling stability (less 5% loss of the maximum specific capacitance after 3000 cycles). The high specific capacitance and charge–discharge rates offered by such MnO₂/Mn/MnO₂ sandwich-like nanotube arrays make them promising candidates for supercapacitor electrodes, combining high-energy densities with high levels of power delivery

Ammonia Electrosynthesis with High Selectivity under Ambient Conditions via a Li⁺ Incorporation Strategy

We report the discovery of a dramatically enhanced N₂ electroreduction reaction (NRR) selectivity under ambient conditions via the Li⁺ incorporation into poly­(<i>N</i>-ethyl-benzene-1,2,4,5-tetracarboxylic diimide) (PEBCD) as a catalyst. The detailed electrochemical evaluation and density functional theory calculations showed that Li⁺ association with the O atoms in the PEBCD matrix can retard the HER process and can facilitate the adsorption of N₂ to afford a high potential scope for the NRR process to proceed in the “[OLi⁺]·N₂H_<i>x</i>” alternating hydrogenation mode. This atomic-scale incorporation strategy provides new insight into the rational design of NRR catalysts with higher selectivity

Porous Pt-Ni-P Composite Nanotube Arrays: Highly Electroactive and Durable Catalysts for Methanol Electrooxidation

Porous Pt-Ni-P composite nanotube arrays (NTAs) on a conductive substrate in good solid contact are successfully synthesized via template-assisted electrodeposition and show high electrochemical activity and long-term stability for methanol electrooxidation. Hollow nanotubular structures, porous nanostructures, and synergistic electronic effects of various elements contribute to the high electrocatalytic performance of porous Pt-Ni-P composite NTA electrocatalysts

Hierarchical Mesoporous/Macroporous Perovskite La_0.5Sr_0.5CoO_3–<i>x</i> Nanotubes: A Bifunctional Catalyst with Enhanced Activity and Cycle Stability for Rechargeable Lithium Oxygen Batteries

Perovskites show excellent specific catalytic activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline solutions; however, small surface areas of the perovskites synthesized by traditional sol–gel methods lead to low utilization of catalytic sites, which gives rise to poor Li–O₂ batteries performance and restricts their application. Herein, a hierarchical mesporous/macroporous perovskite La_0.5Sr_0.5CoO_3‑x (HPN-LSC) nanotube is developed to promote its application in Li–O₂ batteries. The HPN-LSC nanotubes were synthesized via electrospinning technique followed by postannealing. The as-prepared HPN-LSC catalyst exhibits outstanding intrinsic ORR and OER catalytic activity. The HPN-LSC/KB electrode displays excellent performance toward both discharge and charge processes for Li–O₂ batteries, which enhances the reversibility, the round-trip efficiency, and the capacity of resultant batteries. The synergy of high catalytic activity and hierarchical mesoporous/macroporous nanotubular structure results in the Li–O₂ batteries with good rate capability and excellent cycle stability of sustaining 50 cycles at a current density of 0.1 mA cm^–2 with an upper-limit capacity of 500 mAh g^–1. The results will benefit for the future development of high-performance Li–O₂ batteries using hierarchical mesoporous/macroporous nanostructured perovskite-type catalysts