Preparation And Performances Of Metal-based Nanomaterials For Energy Electrocatalysis

The electrochemistry-based new energy conversion and storage is an effective method to solve the current social energy crisis.In fact,the rational design and construction of highly efficient electrocatalysts is the key factor for improving the electrochemical energy conversion performance.The metal-based nanomaterials have drawn a lot of research attention in the field of electrocatalysis because of their unique optical,electrical and catalytic features.And recent studies have proven that the assessment of nanocatalysts is largely defined by the density of active sites and its intrinsic activity.Therefore,the effective and performance optimization-oriented engineering strategies toward metal-based nanomaterials are urgently needed for the fabrication of active and stable catalysts,which in turns to boost the progress of fuel cells and electrocatalytic water splitting.The primary contents and conclusions of this thesis are summarized as following:1.Interfacial engineering of Au@Pd core-shell nanorods with a defined surface structure was successfully achieved via a facile supersaturation tuning method.According to the relationship between the reaction rate and synthetic parameters,supersaturation can be precisely controlled by the pH value,precursor and reducing agent concentration.The surface morphology of the as-prepared Au@Pd bimetallic nanorods transformed from a?111?-facet core-island shell to a?100?-facet core-conformal shell with increasing supersaturation.Electrocatalytic measurement of those core@shell nanorods toward the EOR indicates an obvious“structure-property”relation.Compared with the commercial Pd black catalysts,the conformal-shell and island-shell nanostructures show significantly enhanced electrocatalytic activity and stability toward the EOR in alkaline media,respectively.This work demonstrates a potential possibility of rationally designing and preparing nanomaterials with defined structures and novel functionalities for catalytic reactions.2.A new class of zigzag-like Pt-Zn alloy nanowires bounded with abundant high-index-facets have been successfully synthesized in this work.Composition of these zigzag Pt-Zn nanowires is well controlled by tuning the feeding ratio of Pt/Zn precursor.The as-prepared Pt-Zn nanowires exhibited outstanding catalytic activity and stability toward methanol/ethanol oxidation.Compared with commercial Pt black catalyst,the composition-optimal Pt₉₄Zn₆ NWs shows a 7.2-and 6.2-times enhancement in mass activity for MOR and EOR,respectively.Combination of XPS and XAS analysis reveal that the alloying effect-induced band structure engineering and lattice strain modulation of Pt-Zn NWs weaken the adsorption strength of poisoning species and in turn are responsible for the enhancement in specific activity.This work not only develops a promising catalyst for the alcohol oxidation but also provides the intrinsic explanation for the enhanced catalytic performance.3.A series of highly dendritic Pt-based nanoalloys?Pt-Ni,Co,Fe?were successfully prepared via a general Zn²⁺-mediated solution method and systematic studies were conducted to figure out the growth mechanism.We found that the competition of galvanic replacement between UPD Zn/Pt²⁺and UPD M?Ni,Co,Fe?/Pt²⁺resulted in“branch-to-branch”growth mode,which played a critical role for this morphological engineering.This unique dendritic nanostructure provides fully exposed active sites and the ligand effect downshifts the d-band center and in turn optimizes the H*absorption energy,which endows such alloyed nanodendrites with great potential for HER.Specifically,the as-prepared Pt₃Ni nanodendrites reach a current density of 30.6 mA cm^-2 at-0.07 V vs.RHE,7.4 times higher than that of Pt/C(4.1 mA cm^-2@-0.07 V vs.RHE).This work presents new insights into rational construction of dendritic nanostructure for efficient alkaline HER and beyond.4.We have developed interconnected nanostructure with CoMnP nanodomains and N,P co-doped amorphous carbon grown on carbon cloth?CoMnP-NPC/CC?via a two-step method for HER in alkaline media.Specifically,the as-prepared Co₇Mn₁P-NPC/CC exhibits highly efficient HER activity with an ultralow overpotential of only 48 mV at a current density of 10 mA cm^-2,and a Tafel slope of60.74 mV dec^-1 in 1 M KOH.When the overpotential is more than 93 mV,the Co₇Mn₁P-NPC/CC shows enhanced HER activity compared with the commercial Pt/C.The unique confined growth of both Co MnP active phase and amorphous carbon in a single nanosheet leads to fully interconnected structure,which can provide much more active sites and optimize the electronic structure,contributing to enhancing the catalytic activity.This work offers us new opportunities for the delicate fabrication of highly-efficient nanocatalysts towards not only HER and other catalytic reactions.