Preparation And Electrocatalytic Performance Of Iron/cobalt-doped NiPS₃ Nanosheets

As the cleanest fuel,hydrogen is emerging as an ideal energy carrier and a suitable candidate of fossil fuels in order to settling energy and environmental crisis.So it's significant to looking for an efficiency and sustainable technique to produce hydrogen.Although electrochemical water splitting offers an ideal way for hydrogen production,noble metals are requisite to decrease the energy loss.However,high cost and scarcity of these noble metal-based electrocatalysts severely limit their widespread applications in renewable energy conversion systems.Therefore,a great deal of effort has been made toward cost-effective and earthabundant catalysts as possible alternatives to precious metal materials.In this topic we prepared iron/cobalt-doped few-layer NiPS₃ nanosheets?NSs?as cathodic and anodic electrode catalyst for water splitting.Iron/cobalt-doped NiPS₃ NSs were obtained from solid state reaction under vacuum followed by an ultrasonication-assisted exfoliation process.XRD,Raman,SEM,TEM,AFM and XPS were used to record their crystallographic and micro-structures.Semiconductor analyzer were also used to collect I-V curves of all samples.It turned out that iron/cobalt-doped NiPS₃ have the same structure with NiPS₃.The exfoliated iron-doped NiPS₃ NSs are 5 layers in contrast to 8-10 layers of cobalt-doped NiPS₃ NSs.Iron/cobalt-doped can significantly increase the electrical conductivity which also provide a new way to enhance electrocatalytic activity.The electrochemical measurements were all performed in 1 mol/L KOH aqueous solution.Iron-doped NiPS₃ NSs were used as bifunctional electrode catalyst to catalyze hydrogen evolution reaction?HER?and oxygen evolution reaction?OER?respectively.The result of the test revealed that the dope of iron can dramatically improved catalytic activity of NiPS₃ and Ni0.90Fe0.10PS₃ NSs are the best catalytic both in HER and OER.The optimized Ni0.90Fe0.10PS₃ NSs display a geometric catalytic current density of 10 mA/cm2 at an overpotential of 75 mV vs.RHE and a Tafel slope of 73 mV/dec as cathodic catalytic.And DFT has been used to calculate the hydrogen adsorption free energy ?GH,which has been reported to be a precise descriptor for HER activity.And it is worth noting that when 10% Fe is doped in the NiPS₃,the observed ?GH on the S site is only 0.06 eV.Such smaller ?GH indicated that the Fe doping can significantly affect the HER performance of NiPS₃.An OER current of 20 mA/cm2 is achieved at an overpotential of 329 mV with an exceptionally low Tafel slope of 69 m V/dec.And Ni0.90Fe0.10PS₃ NWs have been oxidized to Ni?OH?2 and NiOOH during OER.Co-doped NiPS₃ NSs were used to catalyze HER,and Ni0.95Co0.05PS₃ NWs displays excellent HER catalytic activity with a low overpotential of 71 mV to achieve a current density of 10 mA/cm2 and a Tafel slope of 77 mV/dec.Therefore,Ni0.95Co0.05PS₃ NSs,a high-performance electrocatalysts for HER,has been prepared.