Construction Of Cobalt-based Nanomaterials And The Application In Electrolyzed Water

With the requirement of green environmental protection and sustainable development,hydrogen production by electrolysis of water has become the development direction of new energy in the future.The application of electrocatalysts can effectively reduce the electric potential required for the electrolysis of water,thereby improving the conversion efficiency.However,due to the limitation of precious metal reserves and cost,it is difficult for traditional precious metal electrocatalysts to be promoted industrially.Therefore,it is urgent to find a new way for the research and development of electrocatalysts.Studies have found that non-noble metal electrocatalysts with transition metals as the core show great development potential.Among them,cobalt-based nanomaterials have been found to exhibit outstanding catalytic activity in OER and HER electrocatalysis,and have been extensively studied.However,at present,most cobalt-based nanomaterials still have a gap in performance compared with precious metal-based electrocatalysts.In addition,there is still controversy about the mechanism of different cobalt-based nanomaterials on electrolysis of water catalysis,so relevant research needs to be further carried out.Based on the above purposes,Cobalt-based nanomaterials were taken as the core of this research,and the noble metal-doped nanomaterials CoRu@NF,heteroatom-doped CoNiP-P@NF and transition metal-doped M-Co-NS@CP(M=Mn?Cr?V)electrocatalysts were deeply dissected from the morphology,structure and properties,respectively,the following conclusions were obtained:(1)Ultra-thin(?1.5 nm)cobalt hydroxide nanosheet array CoRu@NF doped with a trace amount of Ru(1.34 wt%)was prepared by one-step electrochemical deposition.Through SEM and TEM characterization,it was found that the micro-Ru doping significantly changed the morphology of the array of Cobalt hydroxide nanosheets,which inhibited the multi-layer stacking phenomenon of the nanosheets,and promoted the exposure of more surface active sites.At the same time,the atomic dispersion of Ru was verified by XRD and XPS characterization,and the promotion effect of Co-O-Ru bond on the formation of high-value Co was proved.Through the synergistic effect of morphology and structure regulation,CoRu@NF becomes an excellent basic OER catalyst,showing significantly better catalytic performance and excellent stability than RuO2 in alkaline OER catalysis.(2)CoNiP-P@NF catalysts with different phosphorus doping forms were synthesized by two-steps of electrochemical deposition and low temperature calcination,which showed excellent catalytic activity and stability in basic OER and HER catalysis,only 49 mV and 249 mV overpotentials can drive a current density of 10 mA cm-2,respectively,and the required potential is as low as 1.565 V when used for total hydrolysis,which performs well in stability tests for up to 100 h.TEM has verified the existence of a large number of crystalline/amorphous heterogeneous interfaces on the surface of the catalyst.In-depth analysis has been carried out by XRD and XPS.The results show that in the two-step phosphorous doping process,the phosphorous was bonded to the CoNi alloy in the form of phosphate and metal phosphorous bonds.In addition,the formation of phosphate in the electrodeposition process is the key reason for the subsequent formation of the heterointerface of crystalline/amorphous CoO-NiP3 alloy,and the formation of heterointerface effectively promotes the OER and HER catalytic activities of CoNiP-P@NF.(3)Mn?Cr?V doped M-Co-NS powders were respectively successfully synthesized by one-step hydrothermal method.The catalytic activity of different catalysts in alkaline OER was better than that of RuO2.SEM results show that the nanometer flower-like powder was successfully synthesized.The influence of different doping elements on the morphology was analyzed.XRD showed that the doping elements were uniformly distributed in the crystal lattice of cobalt hydroxide.XPS verified the successful synthesis of cobalt hydroxide and the effect of doping elements on the valence state of cobalt.The optimal doping ratio of different doping elements was obtained through the electrochemical performance test.And the effects of various element doping on the OER catalytic activity of M-Co-NS were compared at the same time.