Synthesis Of Cobalt-based Catalysts And Their Performance For Catalysis And Conversion Of Small Energy Molecules

With the rapid development of the world economy and the continuous increase of population,people’s demand for energy continues to increase.The resulting energy consumption and environmental pollution problems are becoming more and more serious.The development of clean and renewable energy conversion technologies is of great significance to solve the current energy and environmental crisis.The use of solar energy or electrical energy converted from solar energy to catalyze and convert small energy molecules has become a hot topic in current research fields.In this paper,cobalt-based molecules and polymerization catalysts were synthesized using the earth-abundant transition metal cobalt,and their photocatalytic CO₂ reduction and electrocatalytic water oxidation performance were studied.The specific research content is mainly divided into the following two parts:1.A dinuclear cobalt-based molecular complex,Co-DPEN,was synthesized by combining Co（II）with bispyridine ethanenaphthyridine（DPEN）through the coordination of six pyridine nitrogen atoms in DPEN.The structure of Co-DPEN was characterized by NMR and mass spectrometry.On the basis of the structural study,the photocatalytic CO₂ reduction performance of the synthesized Co-DPEN was studied,and the reaction conditions were optimized by parallel experiments.Under the optimized conditions,the CO yield is as high as 56μmol,the TON reaches 11218,and the selectivity to CO is 90.3%.In addition,through control experiments and isotope labeling experiments,it was determined that the CO product originates from the reduction of CO₂ catalyzed by Co-DPEN.Finally,a possible mechanism is proposed for the photocatalytic CO₂ reduction by Co-DPEN.2.Using cobalt 5,10,15,20-tetra-4-（trimethylsilyl）ethynylphenyl)porphyrin（Co-TEPP）as the monomer,cobalt porphyrin graphdiyne-like polymer（P-Co-TEPP）was prepared.Bimetallic porphyrins graphdiyne-like polymer（P-Fe₁Co₁-TEPP,P-Fe₁Co₃-TEPP,P-Fe₃Co₁-TEPP）with different cobalt/iron ratios were further synthesized by incorporating different amounts of iron-porphyrin（iron 5,10,15,20-tetra-4-（trimethylsilyl）ethynylphenyl）porphyrin,Fe-TEPP).The obtained materials were characterized by SEM,XPS and Raman et al.Based on the structure and morphology studies,the electrocatalytic water oxidation（OER）performance of the obtained materials was further investigated.The results show that when P-TEPP is loaded with metal,the OER reactivity is significantly improved,and the catalytic activity of cobalt porphyrin graphdiyne-like polymer is better than that of iron porphyrin graphdiyne-like polymer.When the iron porphyrin graphdiyne-like polymer was incorporated into the cobalt porphyrin catalytic center,the OER activity of the obtained bimetallic porphyrin-like graphdiyne polymer material was further improved.P-Fe₁Co₁-TEPP exhibits the highest catalytic activity,with an overpotential of 290m V at 10 m A cm^-2,a Tafel slope of 91.4 m V dec^-1,and good stability.The comparison of electrochemical impedance and Tafel slope shows that the resistance of P-Fe₁Co₁-TEPP is smaller,the charge transfer rate is faster,and thus P-Fe₁Co₁-TEPP has faster OER reaction kinetics.