Synthesis Of Two-dimensional Transition Metal Electrocatalysts And The Performance Of Energy Conversion

Developing novel and sustainable energy resources is an ideal way to solve the problems of energy crisis and environmental deterioration.Converting water and carbon dioxide into clean,high-energy-density fuels such as hydrogen,oxygen and formic acid by electrochemical method can fundamentally solve the energy crisis and satisfy the requirements of sustainable development.Layered bimetallic double hydroxides and transition metal chalcogenides are widely used in the field of electrocatalytic energy conversion due to their low price and abundant metal catalytic sites.Ni-Fe Layered double hydroxides and TaS₂ as well as SnS are widely used for oxygen revolution reaction?OER?,hydrogen revolution reaction?HER?and CO₂ reduction reatcion?CO₂RR?into formate respectively.However,the stacked structure with less exposed active sites and poor electronic conductance limit their further performance improvement.In order to solve these problems,the specific research process is as blew:?1?We developed a novel oxygen-enriched nickel-iron layered double hydroxide?NiFe-LDH?nanosheets electrocatalyst prepared by water-plasma assisted synthesis.The water-plasma engraved oxygen-enriched NiFe-LDH nanosheets possessed a higher ratio of Ni³⁺/Ni²⁺?1.19?and large petal structure of 3?m lateral size with 10 nm thicknesses.Profiting by enriched oxygen atoms and fast charge transfer,the oxygen-enriched NiFe-LDH nanosheets displayed a favorable electrocatalytic performance toward OER with a low Tafel slope of 74mV dec^-1 and an overpotential at 10 mA cm^-2 for 310 mV in 1.0 M KOH.Such low overpotential was much smaller than initial NiFe-LDH nanosheets?360 mV?,and even superior to commercial Ir/C electrocatalyst?370 mV?.?2?We developed two-dimensional TaS₂ ultrathin nanosheets?TaS₂ NSs?prepared by electrochemical exfoliating bulk TaS₂ with an alternated voltage.The obtained TaS₂ NSs possessed an ultrathin structure with a³ nm thickness and a large lateral size of 600 nm.Benefiting from the unique 2D structure and highly exposed active sites,the TaS₂ NSs exhibited remarkable electrocatalytic activity for hydrogen reduction revolution?HER?in acid with a low overpotential of 197 mV at 10 mA cm^-2 and small Tafel slop of 100 mVdec-1,which are much superior than that of bulk TaS₂(extremely more than 547 mV and 216 mVdec^-1)and other TaS₂and transition metal dichalcogenides electrocatalysts.Furthermore,by replacing oxygen evolution reaction with urea oxidation reaction?UOR?,the bifunctional TaS₂ NSs electrocatalysts enable an effective HER process in cathode and UOR process in anode with decreased applied potential.?3?We developed a reliable and scalable electro-exfoliated route,with assistance of alternate voltage,to prepare high-quality two-dimensional SnS ultrathin nanosheets?SnS NSs?,which features a large lateral size of 3?m with a thickness of⁵.0 nm.Systematic electrochemical studies demonstrate the SnS NSs exhibit a highly attractive electrocatalytic property towards CO₂ reduction reatcion?CO₂RR?with a high faradaic efficiency of 74.3%for formate?HCOOH?product,which are higher than those reported for other tin sulfides CO₂RR catalysts.Theoretical calculations manifest the exposed?001?plane of SnS NSs results in high formate selectivity and improved CO₂RR activity.