Construction Of Rare Earth Doped Electrocatalysts And Their Application Performance For Oxygen Evolution

The development of renewable energy sources is urgently needed as the over consumption of fossil energy sources has serious impacts on human societies,including climate warming and the energy challenge.Hydrogen energy is considered the most ideal energy carrier because it is clean and non-polluting.Water electrolysis,as an efficient way to produce hydrogen,is an important means of realizing renewable energy conversion and alleviating environmental pollution.However,the oxygen evolution reaction（OER）from the electrolysis of H₂O is a complicated multiple proton-coupled electron-transfer mechanism and severely limits the development of hydrogen production technology due to its slower reaction kinetics and larger energy barriers.Therefore,the development of OER catalysts with both high stability and superior electrocatalytic properties is a key scientific issue that needs to be addressed urgently.In recent years,rare earth（RE）has received much attention in modulating the performance of OER catalysts mainly due to the unique physicochemical properties and electronic structure,which can effectively adjust the electronic structure.How to design and synthesizeOER catalysts with both high stability and superior electrocatalytic properties of RE/transition metals is the primary task in front of us.In this study,the structure of OER electrocatalysts was modulated by RE doping strategy based on nanostructure engineering to investigate the effect of the modulation on the physicochemical properties of the catalysts and the conformational relationship between the structure and the catalytic performance.The detailed studies are displayed as follows:Firstly,by selecting several typical RE for doping NiCo₂O₄,a facile and effective method for the electronic structure modulation of RE-doped NiCo₂O₄ was designed.Four different RE（La,Ce,Pr,Gd）doped NiCo₂O₄ nanostructured electrocatalysts were successfully synthesized by growing on carbon paper（CP）with a gas-liquid volatilization method at room temperature.It was found that all the RE-NiCo₂O₄/CP electrocatalysts had better electrochemical activity of OER compared to NiCo₂O₄/CP.Among them,Ce-NiCo₂O₄/CP is the best one with the lowest overpotential of 20 mA cm^-2 at only 265 mV.Further mechanistic studies showed that the introduction of RE could increase the ratio of Co³⁺/Co²⁺,especially in the case of Ce,which has strong electronic interaction with Ni and Co.This study provides an effective method to prepare low-cost and highly active RE-doped OER electrocatalysts.Combining the above cerium doping strategy with metal-organic framework（MOF）materials,we systematically investigated the effect of Ce doping on the composition,structure,and catalytic behavior of cobalt-based metal-organic framework（Co-MOF）materials,and developed a novel structural engineering method that can effectively improve theOER performance of Co-MOF.Experimental results and theoretical calculations show that Ce-doped structural engineering achieves the effect of both morphological modulation and electronic structure optimization without changing the MOF structure.Compared with Co-MOF/CP,the Co Ce-MOF/CP exhibited superior OER activity with a low overpotential of 267 mV at 10 mA cm^-2 and stability over 100 h.This work provides new insights into comprehending the RE-enhanced mechanism of electrocatalysis and provides an effective strategy for the design of MOF-based electrocatalysts.Combining the above cerium doping strategy with layered double hydroxide（LDH）,an effective lattice distortion method was developed for the design and synthesis of Ce-doped NiFe-LDH nanoarrays（NiFe Ce-LDH@CP）to boost its OER performance.Ce doping into the lattice enriches NiFe-LDH with structural perturbations and lattice distortions,resulting in a large accessible surface area and inducing moreO_vac,accelerating theOER by modifying the intrinsic electronic structure and optimizing the adsorption energy of intermediates.As a result,the optimized NiFe Ce-LDH@CP possesses excellent stability over 70 h and can deliver the current density of 100 mA cm^-2 with the overpotentials of only 267 mV,which is41 mV lower than pure NiFe-LDH@CP.This work figures out the effect of lattice distortion strategy on the improvement of OER performance,which opens new perspectives on the development of defect-rich OER electrocatalysts.At last,we focused on the OER performance of the cerium compounds and tuned their structure and OER catalytic performance by mutual doping of rare earth elements.A novel Gd doping strategy was designed to improve theOER performance of CeO₂/Ce（OH）CO₃/CF nanosheet hybrids,and the effects of Gd elemental doping on the structure and catalytic behavior of the hybrids were systematically investigated.It was demonstrated that the content of Ce（OH）CO₃,morphology,and oxygen vacancies of CeO₂/Ce（OH）CO₃ nanohybrids can be controlled by changing the amount of Gd doping.Among them,the 2%Gd-doped CeO₂/Ce（OH）CO₃ nanosheet demonstrates dramatically enhanced OER performances with a low overpotential of292 mV at 10 mA cm^-2 and possesses excellent stability over 40 h,outperforming some recently reported Ceria-based OER catalysts.Our findings provide a possible way to develop new electrocatalysts with excellent OER abilities for energy conversion applications.