The Synthesis Of Transition Metal Sulfide And Its Application In Electrocatalysis

It remains an ongoing challenge to develop cheap,highly active and stable electrocatalysts to promote sluggish electrocatalytic oxygen evolution and reduction,hydrogen evolution reactions for rechargeable metal-air batteries and water-splitting systems.Currently,Pt-based metals are recognized as the best ORR/HER catalysts and Ru/Ir-based oxides possess the best OER activities.However,considering their high cost and limited applicability,it remains a great challenge to develop high performance,inexpensive multifunctional alternatives based on earth-abundant elements for the wide-spread applications of the relevant renewable energy systems.Moreover,use of the nanostructuring strategy could further enable the designed electrode materials to have high activity and durability through the optimization of surface configurations,electronic states and morphological architectures,resulting in the fabrication of rechargeable zinc-air batteries and water oxidation devices with high efficiencies and long operational life times.In this paper,we have synthesized two kinds of transition metal sulfide based catalysts with relatively lower cost as well as excellent catalytic properties.In the first work,we demonstrate a novel two-step method of the controllable synthesis of mixed zinc cobalt sulfide?Zn-Co-S?nanostructures?nanosheet?NS?,nanoplate?NP?,and nanoneedle?NN??supported on carbon fiber paper?CFP?substrate and a detailed investigation of the mechanism of morphology synthesis as well as the multifunctional electrocatalytic properties.In the second work,we synthesized Pt nanoparticles?NPs?grown on the surface of CoS₂ nanosheet?demonstrated as CoS₂-Pt/CC?towards advantageous electrocatalysis for both hydrogen evolution reaction?HER?and oxygen evolution reaction?OER?.To gain further insight into the electronic property of the CoS₂-Pt/CC,the strong metal/support interaction?SMSI?between CoS₂ and Pt has been analyzed.The facile electron donation from Co to Pt,leading to the electron-rich structure of Pt,further enhanced the catalytic performances toward both HER and OER.Furthermore,the Zn-Co-S nanoneedle/CFP electrode enables rechargeable Zn-air batteries with low overpotential?0.85 V?,high efficiency?58.1%?and long cycling lifetime?200 cycles?at 10 mA cm^-2 as well as considerable performance for overall water splitting.The superior performance contributes to the integrated nanoneedle nanostructure rooted on CFP,which not only provides enhanced electrochemical active sites but also facilitates ions and gas transfer between catalyst surface and electrolyte,thus maintaining the effective solid-liquid-gas interface.The as synthesized CoS₂-Pt/CC could facilitate the reaction kinetics and deliver efficient and durable electrocatalytic capability,which presented a low voltage of 1.55 V at 10 mA cm^-22 and long time stability for at least 20 h.The electron transformation between Co and Pt lead to an electron-rich structure of Pt,which can promote the adsorption/desorption behavior of intermediates in the electrocatalytic reactions.