Rational Design Of Transition Metal Based Nanomaterials And Their Electrocatalytic Water Splitting Performance

Energy shortage and environmental pollution are the two major challenges facing by human society.The development of new types of clean energy is essential to the country's sustainable development.Hydrogen,with high energy density and pollution-free combustion products,is a promising energy carrier in the future.Electrochemical water splitting to produce hydrogen uses electric energy as an energy driver to extract hydrogen from water.However,at present,the production of hydrogen from electrochemical water splitting is relatively small in industry,and one of the main bottlenecks is the high cost.The high-efficiency hydrogen production catalyst can greatly reduce the energy consumption in the hydrogen production process,thereby reducing the production cost.Under the strategic background of the country's vigorous development of hydrogen energy,the development of high-efficiency and low-cost electrochemical water splitting hydrogen production catalysts is of great strategic significance.The surface and interface of the catalysts are the main places where the catalytic reaction occurs,and the geometric structure and electronic structure at the surface and interface have an important influence on the catalytic performance.Therefore,the development of precise surface and interface control methods is very important for the development of high-efficiency catalysts.In this dissertation,we are aiming to design a low-cost,high-efficiency transition metal-based electrochemical water splitting hydrogen production catalyst.Several surface and interface control methods,such as interface engineering,heteroatom doping,vacancy engineering,and local coordination environment regulation have been developed,and a variety of highly efficient catalysts have been successfully synthesized.At the same time,the fine structure characterization technology is used to study the relationship between the control method and the geometric structure of the material and the electronic structure.Further electrochemical test methods combined with first-principle calculations have deeply studied the relationship between the surface and interface electronic structure and catalytic activity,providing feasible ideas for the design of high-efficiency catalysts.The main contents are listed as follows:1.The research progress of transition metal-based electrochemical water splitting catalysts is briefly introduced.2.Although Ni3N possesses superior hydrogen desorption behavior,its alkaline hydrogen evolution reaction(HER)catalysis is substantially hindered,due to the high-lying unoccupied orbital center induced sluggish water dissociation kinetics.Herein,we successfully endow Ni3N with exceptional alkaline HER activity by in situ interfacial engineering.The prepared Ni3N/MoO2 interfacial system delivers an ultrasiall overpotential of 21 mV at 10 mA cm-2,which is very close to that of the benchmark Pt/C catalysts.Density functional theory(DFT)calculations reveal that MoO2 with a lower unoccupied orbital center could substantially boost the water dissociation kinetics,while the hydrogen desorption proceeds on Ni3N.The capability to understand and design interfacial systems provides an effective pathway for the rational construction of HER catalysts and beyond.3.As an environmentally friendly method of producing hydrogen,electrocatalytic water splitting has attracted worldwide attention.However,its large-scale application has been inhibited by costly catalysts and low energy conversion efficiency,mainly due to the sluggish anodic half reaction,the O2 evolution reaction(OER),whose product O2 is not of significant value.Compared with the extraction of hydrogen from pure water,the production of H2 from biomass derivatives solutions(such as urea,glucose,methanol,ethanol,etc.)is more thermodynamically beneficial.However,the challenge lies in the lack of inexpensive and effective bifunctional catalysts for both H2 production and the oxidation of biomass derivatives.Here we use Ni3N/MoO2 nanosheets as the bifunctional catalyst,achieving the removal from wastewater containing biomass derivatives,which greatly reduces the total energy consumption of H2 production.In fact,the voltage needed to extract H2 in glucosamine solution is significantly lower than that in pure water,which is only 1.20 V.Our results demonstrate the potential of Ni3N/MoO2 nanosheets as efficient bifunctional catalysts for efficient hydrogen extraction from biomass derivatives,and are expected to achieve cost-effective and energy-saving hydrogen production.4.The HER performance of the low cost Co-based phosphides is far from noble metal-based catalysts due to the difference of inherent electronic structures.The most feasible strategy to achieve maximum catalytic performance is to integrate minimum noble metal into Co-based phosphides.However,the precisely control of the coupling sites for on-demand functions and unveiling their underlying interplay for catalysis,is less explored yet technically challenging.Herein,we developed the anion-deficient strategy to precisely control anchoring site of noble metal on CoP2 to achieve maximum catalytic performance.Refined structural characterization reveals that the Ru single atoms(Ru-SAs)specifically bind to the anion vacancies sites,and the coordination environment and electronic structure of central Co are greatly tuned.Theoretical calculation illustrates that the introduced Ru-SAs can not only uniquely modulate the unoccupied d orbital density and energy level of the intrinsic Co sites to boost the water adsorption and activation but also work as an efficient promoter to accelerate water activation and hydrogen production.Impressively,the prepared Ru single atom on anion defective CoP2(Ru-SA/Pv-CoP2)displays an unprecedented overpotential of 6 mV at 10 mA cm-2,and the mass activity is 44.2 times higher than that of benchmark Pt/C catalyst at an overpotential of 50 mV.More importantly,it is demonstrated that orbital modulation induced by the anion-deficient anchored noble metal single atom can generally boost the alkaline HER activities of Pt-SA/Pv-CoP2,which offering a new perspective for the rational design of HER catalysts with maximum atomic economic catalytic performance and beyond.