The Preparation Of Transition Metal-based Nanoarrays Catalysts For Electrocatalytic Water Splitting

The excessive consumption of fossil fuels and the increasing demand for energy,urgent to develop clean and renewable energy.Hydrogen energy is considered as an ideal clean energy due to their high energy density and environmental friendliness.Water splitting is one of the most convenient and economic approach to produce high-purity hydrogen.Nevertheless,the overall efficiency of water splitting is largely impeded due to the high overpotentials of both oxygen evolution reaction（OER）on anode and hydrogen evolution reaction（HER）on the cathode.Currently,noble metal catalysts,such as Pt-based catalyst for HER and Ir-/Ru-based catalyst for OER can be considered as the most outstanding catalyst.However,their high cost and rarity restrict their large-scale commercial application.Besides,the conventional power catalysts fixed on electrode with the help of polymer binder,which would block the exposure of catalytic active sites and reduce the conductivity.Therefore,it is essential yet challenging to develop high activity,conductivity and low cost catalysts.In this paper,we synthesized three transition metal-based nanoarrays catalysts on Ni foam（NF）by simple method.The morphology,components and structure of prepared catalysts were conducted by a series of characterization techniques,and the appropriate formation mechanism was proposed.Besides,we studied their electrochemical performance and stability for HER and OER.The main contents are as follows:（1）Facile synthesis of nanoflower-like phosphorus-doped Ni₃S₂/CoFe₂O₄ arrays on nickel foam as a superior electrocatalyst for efficient oxygen evolution reactionHerein,flower-like phosphorus doped Ni₃S₂/CoFe₂O₄ arrays were generated on three-dimensional（3D）NF（P-Ni₃S₂/CoFe₂O₄/NF）via the two-step hydrothermal treatment and subsequent phosphorization.By virtue of the unique 3D configurations and synergistic effect of multi-compositions,the as-prepared catalyst exhibited greatly improved OER performance in 1.0 M KOH solution,with the overpotential of only254 m V at 50 m A cm^-2 and low Tafel slope of 54.43 m V dec^-1.Besides,a two-electrode system was built by P-Ni₃S₂/CoFe₂O₄/NF and Pt/C/NF performed as anode and cathode,respectively,indicating the superior catalytic for water splitting.This work provides a novel approach for preparing advanced electrocatalyst in energy conversion and storage devices.（2）Iron,manganese co-doped 3D Ni₃S₂ nanoflowers in situ assembled by 2D ultrathin nanosheets on nickel foam as a robust electrocatalyst for oxygen evolution reactionIn this work,Fe,Mn co-doped three-dimensional（3D）Ni₃S₂ nanoflowers were in situ assembled by many inter-connected 2D nanosheets on nickel foam（Fe,Mn-Ni₃S₂/NF）via a hydrothermal and sulfuration steps.By virtue of the unique nanoflower structure and NF as 3D porous conductive substrate,the as-prepared catalyst displayed high OER activity and stability,coupled with a small Tafel slope(63.29 m V dec^-1)and a low overpotential of 216 m V to reach the current density of30 m A cm^-2.This study provides a facile approach for preparing low-cost and efficient electrocatalyst in energy conversion and storage devices.（3）Facile synthesis of iron and rhodium doped Ni₂P nanosheet array supported on nickle foam:An efficient bifunctional electrocatalyst for overall water splittingHerein,Fe,Rh co-doped Ni₂P nanosheets array anchored on self-supported three-dimension（3D）Ni foam（denoted as Fe,Rh-Ni₂P/NF）was prepared via a simple hydrothermal strategy and phosphorization.By virtue of their special sheet nanoarrays structure and 3D porous conductive substrate enable this catalyst display distinguished OER/HER and water splitting activities.It demonstrates a low overpotential of 226 m V@30 m A cm^-2 toward OER and 73 m V@10 m A cm^-2 for HER.Specially,the Fe,Rh-Ni₂P/NF as anode and cathode for overall water splitting with a relatively small voltage of 1.62 V to drive the current density of 10 m A cm^-2.The presented work may provide an alternative option for fabricating the effective bifunctional catalyst for water electrolysis devices.