Preparation And Electrocatalytic Hydrogen Evolution Performance Of Corn Straw Biochar Based Nanomaterials

The efficient treatment and disposal of corn stover has been a pressing challenge in the environmental field.The modification and preparation of corn stover into biochar is an avenue for resource utilization of agro-pastoral waste.Corn stover biochar has potential as a catalytic material,and this study exploits the naturally occurring channel structure in corn stover that conducts water,salt and organic matter to develop it as a novel electrode material for electrocatalysis applications.In this study,two corn stover modified biochar（CSB）electrode materials were prepared using inexpensive corn stover as a charcoal source,and the concept of tortuosity was also proposed for the first time to investigate the evaluation and mechanism analysis of their electrocatalytic hydrogen precipitation performance.（1）In this study,two corn stover modified biochar composite electrode materials（CSB/MoS₂,CSB/Mo₂C）were prepared by different synthesis methods.The linear voltammetric curves（CV）,linear scanning curves（LSV）,double layer capacitance(C_dl),impedance（EIS）and stability curves were obtained by COST electrochemical workstation to analyze and evaluate the electrochemical hydrogen precipitation performance of the corn straw modified biochar composite electrode materials,and combined with scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）and other characterization and analysis tools were used to study the mechanism of electrochemical hydrogen precipitation of corn straw modified biochar composite electrode materials in simulated seawater.The main contents are as follows:（2）Using this method to embed molybdenum into biochar improved the conductivity and stability of composite nanomaterials.CSB/MoS₂ composite nanomaterials were synthesized from the produced modified corn stover biochar and molybdenum source by a one-step hydrothermal method.The high degree of crystallization of 2H-MoS₂ in it,along with the vertical discrete growth of MoS₂ nanosheets on the surface of the biochar,led to a substantial increase in the overall electrical conductivity of the electrode,while the active band edges were fully exposed.The results showed that the lowest overpotential was achieved at 10 m A cm^-2 for the 24 h hydrothermal time,196 and 577 m V for 0.5 M H₂SO₄ and simulated seawater,respectively,due to the simultaneous increase in the number of conductive and active band edges and the decrease in tortuosity,which led to the excellent electrocatalytic hydrogen production performance of the composite nanomaterials.（3）In order to further improve the structure of carbon based electrocatalysts,in this paper,CSB/Mo₂C composite nanomaterials were synthesized in situ using the cold isostatic press technique.The CSB/Mo₂C composite nanomaterials possess superior electrocatalytic hydrogen production performance than the non-in situ synthesized CSB/MoS₂ composite nanomaterials.The results showed that the best performance was achieved at a synthetic ammonium molybdate concentration of 100 g/L,with overpotentials of 48 and 251 m V at 10 m A cm^-2 in 0.5 M H₂SO₄ and simulated seawater,respectively.（4）In order to investigate the mechanism of the influence of the natural pore channel structure existing in biomass on the corrosion resistance of the two composite nanomaterials in seawater,this study demonstrated the existence of large-diameter pore channel structure in the two materials using characterization methods such as high-performance fully automated mercury-pressure instrument and secondary ion mass spectrometry,and combined with the stability of the temporal current curves of the two composite nanomaterials in simulated seawater,it was demonstrated that the large pore channel structure could increase the corrosion resistance of the composite nanomaterials in seawater.