Controllable Preparation And Electrocatalytic Performance Of Transition Metal Phosphides As Oxygen Evolution Reaction Electrocatalysts

With the shortage of energy crisis and the increase of environmental problems,the development of new renewable energy has become increasing urgent.Hydrogen has been considered as the most advantageous alternative traditional fossil energy due to its high energy density and cleanliness.Electrocatalyst-driven water splitting is a mature and promising technology to looking for produce hydrogen,and the reaction does not require high temperature or high-pressure conditions.In large-scale industrial production,KOH is generally used as an electrolyte.Electrochemical water,splitting involves two half reactions,oxygen evolution reaction?OER?and hydrogen evolution reaction?HER?.However,the cathode has high overpotential,which leads to excessive energy consumption.Therefore,an efficient electrocatalyst is needed to decrease the overpotential and improve the efficiency of the oxygen evolution.Currently,IrO2 and RuO2-based materials are the most efficient catalysts for the OER.However,it is difficult to realize large-scale industrialization due to the scarcity and high expense of precious metals.Therefore,the exploration of non-noble-metal catalysts with unexpensive and abundant reserves has been of great interest in science and technology.Herein,carbon-coated transition metal phosphides?CoP/CoP2@NPCNTs and?FeCo?2P@C?with different structure were successfully prepared by using the hydrotalcite-like materials as precursors and subsequent phosphorzation.The electrocatalytic performances of the catalysts for OER were investigated.The thesis focused mainly on the following aspects.?1?Preparation of CoP/CoP₂@NPCNTs composite and their electrocatalytic performances for OER.The.CoP/COP2@NPCNTs composite was prepared via the calcination of the CoAl-LDH/melamine precursor at 700 ? in Ar and the subsequent phosphorization at 500 ? in Ar.Facile visualization by scanning electron microscopy in conjunction with electron backscatter diffraction demonstrates the encapsulation of the CoP/CoP2 nanoparticles within the N,P-codoped CNTs.Electrocatalytic evaluation shows that the composite electrode requires a low overpotential of 300 mV for the OER at 10 mA cm-2 in a 1.0 M KOH solution and,in particular,exhibits an excellent long-term durability of ca.100 h,which is superior to that of the state-of-the-art RuO2 electrocatalyst.Density functional theory calculations reveal that the synergistic effect of CoP and CoP2 can enhance the electrocatalytic performance.?2?Preparation of?FeCo?₂P@C composite and their electrocatalytic performances for OER.We describe a thermally self-generating phosphorization of a host-guest single-source precursor of sodium dodecyl phosphate?SDP?well-intercalated FeCo?OH?2 to prepare echinus-like?FeCo?2P@carbon micro/nanospheres??FeCo?2P@C?as an efficient and stable electrocatalyst for OER.FeCo?OH?2 host provides Co source,and the green and easily available SDP guest serves as bi-molecular sources of P and carbon sources alternate P-sources suitable for the eco-friendly synthesis,and the host-guest interaction enables the P-atom transfer at the molecular scale.The echinus-like?FeCo?2P@C nanospheres exhibits high electrocatalytic activities and good stability for OER,and generated a current density of 10 mA cm-2 at 290 mV when used as a catalyst for OER.Significantly,this host-guest precursor-based synthesis route can be readily extended to prepare?NiCo?2P@C by facilely altering intercalating SDP between binary NiCo?OH?2 and thus greatly boost their electrocatalytic performances.The preparation method is simple,environment-friendly,and high-efficiency,and also provides a new idea for preparing various phosphides.