Design And Performances Investigation Of Carbon-based Nanocomposites Catalysts

The suitable design of metal/carbon material composite catalysts has been shown to achieve the modulation of catalyst selectivity and activity.However,it is still challenging to precisely design and regulate the ligand structure of the active site for a simple and efficient sustainable synthesis of efficient catalysts/electrodes.The development of simple and efficient synthetic routes for the preparation of high-performance catalysts or electrodes still requires a great deal of exploratory work.In this paper,we designed a series of effective and simple synthesis methods,and characterized the morphology,electronic structure and electrochemical properties of the carbon-based composite catalysts.Furthermore,the influence of intrinsic catalyst structure on the selectivity,activity and stability of different catalytic processes has also been further explored.The major research and their results of this paper are shown bolow.1.We demonstrated a one-pot solution synthesis to obtain atomically dispersed platinum（Pt）supported on nitrogen（N）-doped mesoporous carbon（NMC）substrates（Pt/NMC-LT）by conducting the whole synthesis at-40℃,owing to the sluggish nucleation kinetics.We obtained Pt/NMCLT catalyst with superior electrochemical hydrogen evolution reaction（HER）activity and stability,in comparison with NMC supported dominant Pt sub-nanometer clusters catalyst from solution synthesis at RT-25℃（Pt/NMC-RT）and commercial carbon supported Pt nanoparticles catalysts（Pt/C）.Lower over-potential values（only 17.0 and 49.8 mV）were needed for high HER current densities（10 and 100 mA cm-2,respectively）,and no obvious degradation was presented after an accelerated durability test（ADT）for 5000 CV cycles.2.We reported a nitrogen-doped mesoporous carbon supported clustered CoOx composite catalyst（CoOx/NMC）synthesized from the anchored atomically dispersed CoOOH species by an efficient two-step nucleation method.Due to the synergistic and size effects,CoOx/NMC exhibited an enhanced bifunctional electrocatalytic performance in alkaline media than the state of the art commercial Pt/C catalyst for ORR and the OER catalyst（Ir/C）.More importantly,the advanced CoOx/NMC catalyst enabled recharge Zn-air batteries（ZABs）to achieve long-term cycling performance over 400 h by galvanostatic charge-discharge at current density of 10 mA cm-2 with high efficiency,suggesting a very promising alternative to the conventional Pt/C and Ir/C catalysts for an air cathode.3.In this part,a quenching strategy of asymmetric temperature in solution for the rapid generation of vacancy-defect rich clusters was reported.The quenching process could be used to synthesize multitudinous metal compound clusters,including metal oxides,fluorides,oxygen-sulfur compounds,and tungstate.For oxygen evolution reaction（OER）,IrO₂ clusters with abundant oxygen vacancies were obtained and uniformly dispersed in the solution.Compared to commercial IrO₂,the prepared IrO₂ cluster could be directly loaded on carbon paper and used as binder-free electrodes,which exhibited higher OER activity and long-term operational stability in alkaline electrolytes.The quenching strategy provideed a simple and efficient method for the synthesis of clusters,which had tremendous potential for industrial-scale preparation and application,especially further applied to flow electrochemical generators。4.Based on the designed IrO₂+O-XC bifunctional electrode,we created a cyclic oxygen exhalation-inhalation for on-demand and on-site synthesis of H₂O₂ by coupling the OER and the 2e--ORR with a facile alternating-current（AC）electrocatalytic process.By ingeniously manipulating the reaction interfaces and operating voltage,we achieved efficient and stable in-situ production of H₂O₂.The rapid oxygen transfer in the localized three-phase interface favored the sufficient electrochemical reactions.The AC-electrocatalytic system exhibited high performance including H₂O₂ production rate of 40.82 mmol h-1 gcat-1 with Faradaic efficiency of 76.3%under optimized reaction parameter combinations screened by orthogonal experiments.Moreover,such AC-electrocatalysis inspired a new strategy to combine multiple electrocatalytic reactions into one electrode for fundamental study and practical applications.