| Hydrogen energy is rich in the natural world and pollution-free,and it plays an important role in renewable energy and chemical conversion.The surplus electric energy generated by renewable energy such as wind energy,tidal energy,and solar energy is used to drive water splitting to produce hydrogen.This process has attracted wide attention due to its high energy conversion efficiency,high product purity,and low energy consumption.One of the key factors restricting the large-scale development of electrolyzed water is the lack of efficient,stable,and inexpensive catalysts.Noble metal Pt has a small Pt-H bond energy and exhibits excellent performance in the electrolysis of water for hydrogen evolution reaction（HER）.However,Pt is expensive and susceptible to corrosion in alkaline electrolytes.Therefore,there is a need to find low-cost alternatives.Ru has obvious cost advantages over Pt.Ru-H and Pt-H have similar bond energies.Ru-based electrocatalysts are ideal substitutes for Pt for HER,but their stability is poor.By combining highly active Ru with the metal oxide support,the synergistic effect between them can be plenarily exerted,thereby improving the catalytic activity and stability,while further reducing the catalyst cost.Focusing on this,this thesis used a solid-phase reaction strategy to product ruthenium/defect-rich metal oxide composite electrocatalytic materials.While introducing Ru and defects,the metal oxide was modified in terms of morphology,and the catalytic performance and mechanism of the catalyst were also studied.The study mainly consists of the following four aspects:1.The ruthenium/oxygen vacancy molybdenum dioxide composite catalyst was designed with the by the firing process of porcelain.The oxygen vacancies（VO）and metal centers（Ru）were introduced into two-dimensional molybdenum-based catalysts by SPIR strategy.Briefly,this SPIR occurs at the interface between the Mo S2 precursor and the Ru O2 nanoparticles,when the reaction kinetic barrier is overcome at a suitable temperature in an Ar atmosphere.The Ru O2 and the adjacent Mo S2 were in situ converted into Ru and Mo O2,and obtained a composite system（Mi SC-1）with a large amount of active Ru and VO localized on the Mo O2 plane.The SPIR process was tracked and analyzed by in-situ characterization technique and theoretical calculations confirmed the proposed SPIR reaction mechanism.Furthermore,theoretical calculations revealed that synergistic effect of the interface between Ru and Mo O2-VOcan effectively reduce the energy barrier of reaction intermediates for the HER.Mi SC-1 exhibits excellent performance in both electrocatalytic hydrogen evolution and hydrogen production from ammonia borane hydrolysis.2.Based on the solid-phase interfacial reaction strategy,a self-supporting three-phase heterogeneous interfacial catalyst（Ru O2/Ru/Mo O2/CC）was designed and synthesized with carbon cloth as the support.Ru O2/Ru/Mo O2/CC has plenty of hetero-structures structure,it can be applied in the field of water electrolysis.Ru O2/Ru/Mo O2/CC catalyst has rich in various heterostructures.The transmission electron microscopy shows that Ru O2/Ru was uniformly load on Mo O2 arrays.The catalyst shows dual functions of electrocatalytic hydrogen and oxygen evolution reaction in different p H media.Among them,Ru O2/Ru/Mo O2/CC was tested for total water splitting performance in an alkaline electrolyze,and the applied voltage is only1.48 V can reach 10 m A cm-2 current density.This heterointerface can facilitate charge redistribution and optimize the adsorption energy of catalytic reaction intermediates.3.Carbon doping engineering as an attractive strategy,in this work,the ruthenium/carbon-doped molybdenum dioxide composite electrocatalyst（Ru/C-Mo O2）with a three-dimensional porous structure was prepared through a solid-phase redox reaction strategy.This strategy can achieve reverse doping.First,Ru O2 was loaded on the porous Mo2C material.After the solid-phase reaction,the Ru O2 and Mo2C was in-situ transformed to Ru and Mo O2.At the same time,C atoms were doped into the newly generated Mo O2 phase,and the synergistic effect between C-Mo O2 and Ru produced high catalytic activity.The experimental results show that Ru/C-Mo O2 is a catalyst for p H-universal HER,exhibiting overpotentials of 15,36,and 46 m V(10 m A cm-2)in alkaline,acidic,and neutral media,respectively.In 1.0 M KOH,no obvious decay was found after 100 h of i-t test.The experimental and theoretical calculations results reveal the reaction mechanism of the excellent HER performance of the Ru/C-Mo O2 catalyst.C-Mo O2 and Ru lower the energy barriers of hydrogen desorption and water dissociation,respectively,and synergistically promote the overall catalytic performance.4.The VO-rich crystalline/amorphous WO3 with Ru NPs loading composites（Ru/WO3）were designed and prepared through a solid-phase redox reaction strategy.Crystalline/amorphous WO3 provides abundant VO,with the synergistic effect between WO3-VO and Ru NPs promoting electron transfer,so that the electronic structure of the material can be regulated,and more active sites are exposed to improve the overall catalytic activity.At the same time,the crystalline phase WO3 carrier can stabilize the crystal structure,and ensure that the catalyst still maintains a high catalytic activity during long-term cycling.Ru/WO3 exhibits outstanding HER electrocatalytic performance in alkaline electrolyte solution,with a Tafel slope of 35.8 mv dec-1,and an overpotential of only 10 m V at a current density of 10 m A cm-2,which is even better than some reported noble metal Pt-based materials.At the same time,Ru/WO3 also showed excellent ORR electrocatalytic performance in oxygen-saturated 0.1 M KOH,with an oxygen reduction half-wave potential of 798 m V.Ru/WO3 exhibits excellent stability both in HER and ORR.Theoretical calculations results indicate that Ru and VO-rich crystalline/amorphous WO3 synergistically reduce the reaction energy barrier,which leads to the excellent electrocatalytic performance of Ru/WO3. |
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