The Preparation Of Transition Metal Nanoarray Materials And Their Electrocatalysis And Photoelectric Sensing Research

At present,the development of society depends heavily on fossil fuels.However,the excessive consumption of fossil fuels has caused a series of environmental problems and energy crisis.Therefore,the development of new energy resources to replace the old ones is a great urgency to be solved.Hydrogen and ammonia,as environmentally friendly and renewable clean energy resources,still suffer from issues,such as,high energy consumption,severe pollution and harsh synthesis conditions in the production of modern energy industry.Most importantly,the preparation of clean energy by electrochemical method is the most promising approach.Of note,the catalysts with high catalytic activity and long-term stability are the most essential part of such approach.Noble-metal based catalysts possess efficient catalytic performance,but the high price,scarce reserves and poor stability limit their wide application.In recent years,the transition-metal based nanomaterials were employed to replace the noble-metal based catalysts due to their unique electrochemical properties.On the other hand,such transition-metal based nanomaterials are enable to enhance the surface-interface behaviors such as specific adsorption,aggregation or catalysis of surface species.In addition,they can improve the photocatalytic and electrocatalytic performance,and the ability of highly sensitive analysis and detection.Therefore,the transition-metal based nanomaterials are often combined with nanoscale biotechnology and fluorescence,photoelectrochemistry and other analytical methods to achieve high sensitivity detection of disease markers,and provide theoretical basis and solutions for diagnosis,environmental and food monitoring and other important issues.This work focuses on the research of catalysts in synthesis,characterization,water splitting,electrochemical nitrogen reduction reaction and photoelectrochemical biosensors.The main researches are as follows:?1?We prepare the Ni?OH?₂ nanoparticles embedded in tetracyanoquinodimethane?TCNQ?microrod array on copper foam?Ni?OH?₂-TCNQ/CF?by low-temperature hydrothermal method,ambient ion exchange method and anodic oxidation method.As a 3D electrode,such Ni?OH?₂-TCNQ/CF shows superior electrocatalytic property with low overpotentials of only 322 and 354 mV to afford geometrical catalytic current densities of 50 and 100 mA cm^-2 in 1.0 M KOH,respectively.In addition,it also demonstrates strongly long-term electrochemical stability with its performance being kept for at least 20 h.The Ni?OH?₂-TCNQ/CF catalyst is better than most non-noble-metal catalysts documented in literature under alkaline condition and the main reasons are as follows.First,introducing the TCNQ increased the conductivity of the catalyst;Second,the Ni?OH?₂ nanoparticles embedded in TCNQ microrod array made them difficult to aggregate,thus exposed more active sites.Third,the 3D structure increased the electrode stability,lowered the series resistance,exposed more active sites,and facilitated the diffusion of electrolyte and gas.?2?We synthesized the Fe?tetracyanoquinodimethane?₂ nanorod array on copper foam?Fe?TCNQ?₂/CF?via low-temperature hydrothermal method and low-temperature cationic exchange method.Firstly,Cu?tetracyanoquinodimethane?nanorod array grown on copper foam?Cu?TCNQ?/CF?was prepared by low-temperature hydrothermal method.And then the Cu?TCNQ?/CF was immersed in solution containing Fe²⁺.In this process,Fe²⁺exchanged with Cu⁺in Cu?TCNQ?/CF to fabricate Fe?TCNQ?₂/CF.Serving as a conductive electrode for water electrolysis,such postsynthetic ion exchange of Fe?TCNQ?₂/CF gives obviously enhanced OER performance with low overpotentials of 321 and 353 mV at 20 and 50 mA cm^-2 in 1.0M KOH,respectively.In addition,it has excellent long-term catalytic stability with its performance being kept for 25 h at lowest.?3?NH₃,as a green energy carrier,potential transportation fuel and chemical for fertilizer synthesis,plays an indispensable role in the agricultural,plastic,pharmaceutical and textile industries.Currently,industrial NH₃ synthesis still highly relies on the conventional Haber–Bosch process using heterogeneous iron-or ruthenium-based catalysts at high temperature?300–500??and high pressure?150–300 atm?,which accounts for over 1%total global fossil energy and causes more than300 million metric tons of CO₂ emissions annually.We synthesized the zero-valence Cu nanoparticles anchored on reduced graphene oxide?Cu NPs-rGO?by simple two-step method as an efficient catalyst for electrochemical nitrogen reduction reaction?NRR?.As a superior NRR electrocatalyst for ambient N₂-to-NH₃ conversion process,the as-obtained Cu NPs-rGO achieves a large NH₃ yield rate(V_NH3)of 24.58?g h^-1mg^-1_cat.and a high Faradaic efficiency?FE?of 15.32%at-0.4 V vs.reversible hydrogen electrode?RHE?in 0.5 M LiClO₄.Moreover,such electrocatalyst exhibits high electrochemical stability and superior selectivity.The excellent NRR performance is due to:The large surface area of rGO can prevent the agglomeration of Cu nanoparticles and expose more active sites;The rGO can further enhance the conductivity of Cu;Theoretical calculations demonstrated that zero-valence Cu catalysts can be compared favorably to oxidized Cu materials in forming?backdonation which is conducive to adsorption and activation of nitrogen.?4?WS₂ nanowire array on Ti mesh?WS₂ NW/TM?as a photoelectrochemical?PEC?biosensor for highly sensitive detection of breast cancer biomarker human epidermal growth factor receptor-2?HER2?is reported.We adopted a dual signal amplification strategy.Gold nanoparticles?Au NPs?modified with glucose oxidase?GOx?and HER2 specific peptide were utilized for signal amplification.Such bioconjugates can be captured by the HER2 aptamer wrapped nanowire array.The GOx can catalyze glucose to produce H₂O₂,which as a sacrificial electron donor can scavenge the holes generated on the valence band of WS₂ NW/TM and thus amplifies the PEC signal.In addition,the introducing of the localized surface plasmon resonance of Au NPs into PEC system can also enhance photoelectric transfer efficiency and increase the photocurrent response as well.In such system,dual signal amplification was achieved,leading to high sensitivity of the sensor.The reported signal amplification method can be adapted to other PEC sensors and has a great potential for clinical and biological analysis.?5?We reported the CuO/Cu₂O nanowire array supported on copper foam?CuO/Cu₂O NW/CF?as photocathode for detection of tyrosinase though quinone-chitosan conjugation chemistry method.Such method can directly immobilize the electron accepter on the surface of the electrode,which increased the chance of collision between the electron acceptor and the surface of the electrode,and thus improved the sensitivity.During the illumination process,the electrons on valence bands of both Cu₂O and CuO are excited to their conductive bands,resulting in the holes on their valence bands.The excited electrons on conductive band of Cu₂O are injected to that of CuO and consumed by the quinones immediately.The holes on the valence band of CuO are transferred to that of Cu₂O and scavenged by the electrons from conductive copper foam.In such process,the quinones immobilized on electrode surface will efficiently capture the electrons and thus improve the sensitivity of the biosensor.The proposed biosensor can realize a rapid response in a wide linear range of 0.05 U/mL to10 U/mL with the detection limit as low as 0.016 U/mL.