The Synthesis Of Transition Metal Compounds Anchored On Carbon Cloth And Their Application In Water Electrolysis

Due to the increasing demand of energy and the rise of concern about the environment,much more attention has been focused on developing a green renewable energy resource.Hydrogen（H₂）,as a clean energy carrier with high energy density,is one of the promising substitutions for fossil fuel that has the potential to alleviate global energy crisis.Hydrogen can be conveniently achieved from electroreduction of water.However,water electrolysis requires highly active and robust catalysts.The noble metals and their oxides can be regarded as the best electrocatalyst for hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）,which are both restricted by their scarcities and high costs for large-scale applications.Recently,earth-abundant non-noble metal compounds have emerged as novel electrocatalysts to accelerate water splitting.These transition metal compounds will hopefully become an inexpensive alternative to precious metals in the efficient electrolysis of water.Studies have shown that the combination of two transition metal compounds can enhance the electrocatalytic performance of the catalyst due to its electrocatalytic synergy or charge redistribution.Furthermore,carbon cloth（CC）,a three-dimensional conductive substrate,could not only offer strong adhesion and reduced interfacial impedance to promote electrochemical activity of catalysts,but also provide flexible substrates on which catalysts grown as flexible electrodes,which is important for the development of portable hydrogen device.Herein,we report a two-step method for the fabrication of CoS₂/CoP or NiS/Ni₂P anchored on carbon cloth（denoted as CoS₂/CoP/CC）.First,the precursor was uniformly distributed in CC fibers after the hydrothermal reaction.The second step,CoS₂/CoP or NiS/Ni₂P hybrid materials were obtained through the phosphorization and sulfurization.Then we investigated the morphology and structure of the hybrid materials,and further explored the relationship between their microstructure and the catalytic performance.（1）CoS₂/CoP hybrids based on carbon cloth were prepared through hydrothermal method and chemical vapor deposition method.The CoS₂/CoP clusters vertically grown on the surface of the carbon cloth fiber with a high crystallinity.The CoS₂/CoP/CC hybrids were directly used as a working electrode in alkaline electrolyte and the electrochemical tests demonstrated they had excellent performances both on the HER and OER.It is believed that the redistribution of charge in the CoS₂/CoP/CC hybrid would be an important role for the enhanced catalytic performance.（2）The precursor containing Ni anchored on carbon cloth were obtained by hydrothermal method.And then the NiS/Ni₂P/CC hybrids were fabricated after the phosphorization and sulfurization of the precursor.There were many nanosheets with large diameter growing on carbon cloth fiber vertically,on which NiS and Ni₂P with high crystallinity.In the alkaline solution,the results of electrochemical tests revealed that the hybrids exhibiting significantly enhanced catalytic activity of HER and OER.The overpotential of NiS/Ni₂P/CC hybrids is only91 mV in HER,and the slope of Tafel is approximately 103.9 mV dec^-1.More active edge sites were exposed on the nanosheets after the phosphorization and sulfurization,which can result in significantly enhanced catalytic activity.The formation of NiS/Ni₂P hybrid produced the Ni-sites that gathered large electrical charges,which is another reason for the improved catalytic activity.