Synthesis Of Carbon/Metal Composite And The Study Of Their Photo/Electric Catalytic Properties

The development of renewable energy is an ideal technology for replacing fossil feedstock and handling energy crisis and their adverse effects on climate and environmental consequences.However,the critical bottlenecks for synthesize of renewable energy are the impractically high activation energy required to drive reaction and the low selectivity for diversiform products.Transition metals and their oxides,such as gold,copper and cobalt,have been applied in various photo-and electric-catalytic fields due to their high stability,easy functionalization and distinctive photo/electric properties.In recent years,the structure and application of carbon materials are blooming.Carbon materials,including carbon dots,carbon nanotubes,graphene,carbon nitride and enzymes,are mainly used in the field of catalytic research.However,the electrocatalytic properties of metal materials and carbon nanomaterials sill need to be further studied.This paper introduces preparation of laccase-Au hybrids,Cu-CDots nanocorals electrocatalyst and CO3O4-CDots-C3N4 composite.The structures of these materials were characterized with many instruments,such as transmission electron microscopy,X-ray photoelectron spectroscopy and X-ray powder diffraction.Besides,their photo/electro-catalytic activity and corresponding catalytic mechanism of these materials were also studied.The detailed contents are shown as follows:(1)Laccase-Au hybrids with relatively high activity(increase by 91.2%)was prepared by a simple method.Under 3 min of illumination,the activity of laccase-Au hybrids decreases by 8.1%(vs laccase-Au hybrids without light),but it can be restored to its initial activity when the light resource was removed.The activity of laccase-Au hybrids is reversible with short time illumination.However,long irradiation has an irreversible effect on the activity of laccase-Au hybrids.Green light(500-560 nm)has the greatest impact on the activity of laccase-Au hybrids.The LSPR of Au NPs causes the structure change and local high temperature near the Au NPs.Those changes eventually affect the transportation of electrons in laccase,resulting in the activity decline.(2)Cu-CDots nanocorals was synthesized by sol-gel method and electroreduction.It is a highly efficient,lowcost and stable electrocatalyst for CO2 reduction in aqueous solutions.The major product of CO2 reduction on the Cu-CDots nanocorals is HCOOH with an inconceivable low overpotential of 0.13 V and FEs of 79%at a moderate potential of-0.7 V.Cu-CDots nanocorals exhibit a long-term stability during 5 h-electrolysis.We propose insights into the role of CDots on the increased activity of the Cu-CDots nanocorals electrocatalyst for CO2 reduction.This may be ascribed to the fact that CDots have an enhanced adsorption capacity for the CO2 molecule and the HCOOH desorption energy on Cu-CDots nanocorals can be diminished because of the modification to the CDots.(3)The design concept of the HER-CDots-C3N4 composite EC catalyst for syngas production was introduced and its electrocatalytic performance for syngas production in aqueous solutions was studied,applying CO3O4,MOS2,Au and Pt as the HER catalyst component.The CO3O4-CDots-C3N4 composite electrocatalyst was found the most efficient for syngas production among the composite combinations investigated.The CO3O4-CDots-C3N4 commposite is capable of controlling the balance between the HER channel and CO2 reduction channel.The CO3O4-CDots-C3N4 composite initiates the reaction of CO2 reduction to CO in aqueous solutions at a low overpotential(0.17 V vs.RHE)while the total current density reaches up to 15 mA/cm2 at a potential of-1.0 V vs.RHE.The CO3O4-CDots-C3N4 composite induces high FEs(95%)and is characterized by a stable production of syngas(over 100 h).Notably,the H2/CO ratio of syngas produced applying CO3O4-CDots-C3N4 is tunable from 0.07:1 to 4:1 by controlling the applied potential.The H2/CO may be also tuned by varying the amount of CO3O4 in the CO3O4-CDots-C3N4 composite.