Interface engineering of mesoporous triphasic cobalt-copper phosphides as active electrocatalysts for overall water splitting

Efficient electrocatalysts for water splitting are essential for viable generation of highly purified hydrogen. Hence there is a need to develop robust catalysts to eliminate barriers associated with sluggish kinetics associated with both anodic oxygen and cathodic hydrogen evolution reactions. Herein, we report a two-step nanocasting-solid phase phosphorization approach to generate ordered mesoporous triphasic phosphides CoP@Cu2P-Cu3P. We show that it is a highly efficient bifunctional electrocatalyst useful for overall water splitting. The mesoporous triphasic CoP@Cu2P-Cu3P only requires a low overpotential of 255 mV and 188 mV to achieve 10 mA cm(-2) for oxygen and hydrogen evolution reactions, respectively. The combination of mesoporous pores (similar to 5.6 nm) with very thin walls (similar to 3.7 nm) and conductive networks in triphasic CoP@Cu2P-Cu3P enable rapid rate of electron transfer and mass transfer. In addition, when CoP@Cu2P-Cu3P is used to fabricate symmetric electrodes, the high surface area mesoporous structure and synergetic effects between phases together contribute to a low cell voltage of 1.54 V to drive a current density 10 mA cm(-2). This performance is superior to noble-metal-based Pt/C-IrO2/C. This work provides a new approach for the facile design and application of multiphase phosphides as highly active bifunctional and stable electrocatalysts for water-alkali electrolyzers

Supporting nickel on vanadium nitride for comparable hydrogen evolution performance to platinum in alkaline solution

The hydrogen evolution reaction (HER) is an effective means to producing hydrogen from electrolytic water splitting. However the best-performing catalysts use expensive Pt-group metals. Cheaper non-precious metal alternatives have shown low activity as their mechanism of H-2 formation (Volmer-Heyrovsky) leads to high overpotentials. Here, we report an outstanding HER catalyst (Ni/VN) highly dispersed nickel supported on vanadium nitride that matches the turnover frequency of the platinum on carbon (Pt/C) benchmark material. It is more durable than Pt/C in alkaline solution. Ni/VN follows the low-overpotential (Volmer-Tafel) mechanism of H-2 formation, with a 43 mV overpotential at a current density of 10 mA cm(-2). This value is even below that of Pt/C (57 mV). The support of VN enhances the dispersion of nickel, weakens the surface oxidation, decreases the hydrogen binding energy, and therefore significantly improves the HER catalysis. This result removes one of the major barriers for scalability of electrolytic water-splitting by demonstrating that nitride-based materials can match and even surpass the efficiency and durability of precious metal catalysts

Selective and Continuous Electrosynthesis of Hydrogen Peroxide on Nitrogen-doped Carbon Supported Nickel

Hydrogen peroxide is a widely used industrial oxidant, the large-scale production of which continues to be done by an indirect process. Direct electrosynthesis of hydrogen peroxide from aerial oxygen and water is a sustainable alternative, but this remains challenging because hydrogen peroxide is highly reactive and robust catalysts are vital. Here, we report direct and continuous electrosynthesis of hydrogen peroxide under alkaline conditions using a nitrogen-doped-carbon-supported nickel catalyst. Both experiment and theoretical calculations confirm that the existence of nickel particles suppresses the further reduction of hydrogen peroxide on Ni-N-C matrix. In air-saturated 0.1 M potassium hydroxide, the energy-efficient non-precious metal electrocatalyst exhibits a consistent Faraday efficiency over 95% at a steady rate of hydrogen peroxide production (15.1 mmol min−1 gcat−1) for 100 h. This sustainable, efficient, and safe process is an important step toward continuous production of hydrogen peroxide

Review-Wearable Graphene Devices for Sensing

Graphene has become one of the most readily used materials in wearable sensing technology due to its unique properties of lightweight, ultrahigh carrier mobility, good environmental stability and robust mechanical flexibility. However, efforts based on graphene have still rarely been made for fabricating device-level wearable sensors. In addition, few review articles related to these aspects have been reported. In this work, recent research progress of wearable graphene sensors for healthcare, motion detections, and environment monitoring, is briefly reviewed. Also, the challenges and perspectives for the future generation of wearable graphene sensors are also highlighted. This work provides a comprehensive understanding on the present research situations and challenges for wearable graphene devices for sensing. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited

Conductive Holey MoO2-Mo3N2 Heterojunctions as Job-Synergistic Cathode Host with Low Surface Area for High-Loading Li-S Batteries

Conductive Holey MoO2-Mo3N2 Heterojunctions as Job-Synergistic Cathode Host with Low Surface Area for High-Loading Li-S Batterie

Recent Advances in Nanocasting Cobalt-Based Mesoporous Materials for Energy Storage and Conversion

The generation of novel mesoporous materials with well-defined structure and accessible pore networks is helpful in both fundamental and energy-related research. Nanocasting mesoporous earth-abundant materials and their composite materials offer opportunities to make electrochemically active materials that allow scalable production and cost-effectiveness. Recently, due to their intrinsic open pore structure as well as high surface areas, various mesoporous cobalt-based ordered materials have been applied to electrocatalysis, rechargeable batteries, and supercapacitors. In this review, we have critically evaluated the advancements made specifically in three- and two-dimensionally (3D/2D) electrode Co-based materials (oxides, nitrides, phosphides, and sulfides). We outline foreseeable challenges and issues for the utilization of mesostructured cobalt-based electrode materials. This review also provides guidelines for further work to those who work on energy-related applications of mesoporous cobalt-based materials

Tungsten-Nitride-Coated Carbon Nanospheres as a Sulfur Host for High-Performance Lithium-Sulfur Batteries

Tungsten-Nitride-Coated Carbon Nanospheres as a Sulfur Host for High-Performance Lithium-Sulfur Batterie