Surface Regulation Of Pt Based Noble Metal Catalysts For Electrocatalytic Water Splitting

Hydrogen energy is considered as a primary carbon-neutral energy carrier to replace fossil energy,due to its merits of environmental friendliness,renewability,and high energy density.Water electrolysis,potentially driven by renewable energy,has great application prospect.To date,noble-metal electrocatalyst is widely used for electrocatalytic water splitting due to their unique physical and chemical properties,but their high cost and scarcity hinder the large-scale use of such catalysts.Therefore,designing suitable composition,structure and morphology can reduce the amount of noble metal and improve the utilization of atoms.Moreover,various surface interface regulation strategies can be used to increase the number of active sites and the intrinsic activity of each active site,thus improving the catalytic performance of noble metal nanocatalyst.In this paper,many advanced strategies,including heteratomic doping,surface disorder and noble metal alloying,are proposed for precisely regulating the electronic structure,coordination environment and orbital energy level of Pt-based nanocatalysts.Meanwhile,the relationship among the regulation,electronic structure and performance is studied by fine structure analysis,electrochemical testing and theoretical calculation,which provides important insights for the design of noble metal electrocatalysts.The specific research content of this paper is as follows:1.N-induced orbital modulation can boost the alkaline HER activities of Pt-Ni nanowires.The N-element doping modification Pt-Ni nanowires(Pt-Ni(N)NWs)is synthesized by solvothermal and ammonia calcination method.The prepared Pt-Ni(N)NWs can deliver an ultralow overpotential(η)of 13 mV at the current density of 10 mA cm-2.N with small atomic radius can be easily incorporated into the interstices of Pt-Ni during ammonia treatment.Fine structure analyses indicate N can specifically bind to the Ni sites and further essentially modulate the electronic and coordination structures of Pt-Ni.Theoretical calculation reveals the incorporation of N can effectively regulate the electron density around the Ni sites,further create empty dz2 orbitals with superior orientation for water adsorption and activation.Therefore,N-induced orbital modulation can accelerates the water dissociation kinetics on the Pt-Ni surface and boosts the alkaline hydrogen evolution(HER)performance.2.The surface-disordered engineering can effectively mediate the electronic structure and orbital energy level of Pt-Ni NWs for improving the alkaline HER performance.The Pt-Ni NWs with surface atomic disordering(d-Pt-Ni NWs)were synthesized by solvothermal and lithium/de-lithium method.The lithium atoms inserted or deposited on the surface of Pt-Ni during the lithiation process can be removed by washing with ultra-pure water.Meanwhile,the vigorous reaction between the lattice-interstitial Li atoms and water molecules could lead to the crystal lattice expansion and disordering,which consequently introduces abundant defects and coordination-unsaturated sites at the nanowire surfaces.The optimized d-Pt-Ni NWs achieve an impressive overpotential of 15 mV at 10 mA cm-2,which is substantially better than the pristine Pt-Ni NWs and commercial Pt/C catalysts.Fine structural analyses reveal that the structural disorder can well regulate the electronic structures of Pt-Ni and the generated oxygenated nickel species contribute to stabilize the disordered structures.Furthermore,theoretical studies unravel that the oxygenated nickel with lower unoccupied orbitals facilitates the water adsorption and dissociation,while the upshift of the d band center of Pt enables superior H adsorption.Therefore,the synergistic effect of these two factors promotes the alkaline HER performance.3.Alloying strategy is applied to regulate the electronic structure of IrPt nanoparticles and improves their acidic oxygen evolution(OER)performance.The Ultra-small IrPt alloy nanoparticles(IrPt NPs)are synthesized by a simple and convenient solvothermal method with ethylene glycol as reductant.IrPt NPs show excellent OER catalytic performance under acidic conditions,delivering the overpotential of 243 mV to obtain a current density of 10 mA cm-2.The morphology and structure analysis show that the size of IrPt NPs is very small(-2 nm),and a specific wide peak exists in the X-ray diffraction(XRD)pattern.The ultra-small particle exposes more active sites and higher intrinsic activity.Fine structure analysis shows that the electronic coupling between Pt and Ir atom optimizes its electronic structure and improves the adsorption behavior of intermediate.The electrochemical tests exhibit that the alloyed Pt can improve the reaction kinetics and charge transfer,thus improving the OER catalytic activity of IrPt NPs.Additionally,the electrolytic cell with IrPt NPs as cathode and anode catalyst also shows excellent performance for water splitting,providing a cell voltage of 1.466 V at 10 mA cm-2 and long-term stability.