Heteroatom-Doped Vertically Oriented Graphene Nanosheets With Plated Iron-Group Metal Borides As High-Performance Composite Catalysts For Electrocatalytic Hydrogen

With the increasingly serious environmental problems and energy crisis,the exploration of new environment-friendly energy has become an urgent task for social development.Clean and renewable hydrogen is considered as one of the most desirable alternatives to traditional fossil energy in new energy.Among the technologies of hydrogen generation,water electrolysis is regarded as a fascinating method due to its high efficiency and non-pollution.However,the decomposition of water is not thermodynamically favored,highly efficient electrocatalysts is required to reduce the overpotential of water electrolysis.Currently,noble metal catalysts,such as Pt and Ir O₂/Ru O₂ exhibit most efficient electrocatalytic activity for Hydrogen evolution reaction（HER）and Oxygen evolution reaction（OER）,limit for practical applications owing to their high cost and scarcity.Thus,it is highly essential to develop a cost-effective earth abundant and non-precious metal based electrocatalyst for overall water splitting with improved catalytic activity.Herein,we develop a facile method for the fabrication of novel iron group metal borides/boron-doped vertically oriented graphene（IMBs/BVG）electrocatalyst via single-step electrodeposition approach for overall water splitting over a wide p H range（acidic,neutral and basic）.In addition,the practical application of metal/heteroatom-doped vertically oriented graphene（M/HVG）composite for environmental monitoring was explored subsequently.We develop a novel acetylcholinesterase（ACh E）biosensor based on gold nanoparticles/nitrogen-doped vertically oriented graphene（Au NPs/NVG）composite for the detection of organophosphorus pesticides（OPs）in real samples.1.Boron-doped graphene（BG）was synthesized using a hydrothermal method.The IMBs/BVG composite catalyst was prepared by single-step electrodeposition of BG.The morphology,composition,and structure of IMBs/BVG catalyst were characterized by scanning electron microscope（SEM）,X-ray diffraction（XRD）,and X-ray photoelectron spectroscopy（XPS）.The electrocatalytic performances of IMBs/BVG catalyst were further investigated by electrochemical measurements.The as-synthesized electrocatalyst exhibited excellent hydrogen evolution reaction（HER）activities with low overpotentials of 41,140,and 168 m V at a current density of 10 m A cm^-2 in 1.0 M KOH,0.5 M H₂SO₄,and 1.0 M phosphate buffer solutions（PBS）,respectively at all p H values（p H 0-13.8）.Fe-Co-Ni-B/BVG electrocatalyst also exhibited excellent oxygen evolution reaction（OER）activities with overpotentials of 163,570,and 110 m V at a current density of 10 m A cm^-2in 1.0 M KOH,0.5 M H₂SO₄,and 1.0 M PBS solutions,respectively.This electrocatalyst also showed prominent electrochemical durability（over more than 10 h）.This study may provide a facile design for the fabrication of novel bifunctional IMBs/BVG electrocatalysts for overall water splitting withstand in different p H conditions.The overpotentials and Tafel slopes of IMBs/BVG electrocatalyst for overall water splitting were superior to most of the previously reported non-noble metal bifunctional electrocatalysts.The IMBs/BVG electrocatalyst exhibited satisfactory catalytic activity for overall water splitting over a wide p H range.2.In addition,the novel material based on VG was prepared via single-step electrodeposition for environmental monitoring.Nitrogen-doped graphene（NG）was synthesized using a heating reflux method.The Au NPs/NVG composite was prepared by single-step electrodeposition of NG.The particle size and structure analysis of Au NPs/NVG composite were characterized by SEM,energy dispersive spectrometer（EDS）,and Raman spectra.Then,ACh E was favourably modified on the surface of Au NPs/NVG composite through Cysteine（Cys）.Finally,the ACh E/Cys/Au NPs/NVG biosensor was successfully prepared.The electrochemical sensing performances of as-prepared biosensor were observed by electrochemical measurements.Under optimum conditions,the results displayed high sensitivity of the derived biosensor for monitoring malathion and methyl respectively.The recoveries varied from 94.0%to 106.0%in the detection of tap water,distilled water,and apple samples.The ACh E/Cys/Au NPs/NVG biosensor also revealed operational stability,satisfactory reproducibility,good recovery,and potential practical applicability.