Construction Of Layered Nickel-iron Hydroxide-based Composites Based On Electrostatic Self-assembly And Their Electrocatalytic Propreties

Oxygen evolution reaction?OER?,as a crucial part of the energy conversion reaction,has a wide range of applications in renewable energy technologies such as water splitting,and it has led to many studies in recent years.However,OER at the anode has been regarded as the main bottleneck due to the sluggish kinetics and large overpotential.Hence,it is necessary to construct and design an OER electrocatalyst with a lower overpotential to improve the energy conversion efficiency.Current research indicates that noble metal oxides?IrO₂ and RuO₂?are considered to be the best OER electrocatalysts,but the high cost and poor resources limit their further applications.Therefore,it is necessary to develop non-noble metal OER electrocatalysts with low cost and high catalytic activity.Layered double hydroxide?LDH?shows a huge application potential in this field due to its unique two-dimensional structure and good intrinsic OER activity.Therefore,this paper takes NiFe-layered double hydroxide?NiFe-LDH?as the target material,and prepares a series of electrode materials with high OER catalytic activity through exfoliation-assembly strategy.The main research contents and related conclusions of this paper are as follows:?1?An environment-friendly and efficient solid-phase exfoliation strategy was developed to achieve the complete exfoliation of NiFe-LDH and graphene oxide?GO?,and NiFe-LDH/RGO?NFRG?nanohybrids were prepared by further electrostatic assembly.The results of various characterizations show that compared with the traditional liquid phase exfoliation,this kind of solid-phase exfoliation strategy has a high exfoliation efficiency,and it can reach at least 10 wt%and 5 wt%exfoliation efficiency for NiFe-LDH and GO,respectively,and this method provides a new train of thought for the exfoliation of two-dimensional?2D?materials.In addition,the assembly of NiFe-LDH and GO can form composites with different heterostructures,in which NiFe-LDH nanosheets can be tiled horizontally or stand vertically on GO nanosheets;The standing assembly with an open array structure shows excellent OER activity(with a small overpotential of 273 mV at the current density of 30 mA cm^-2 and a Tafel slope of 49 mV dec^-1).The catalytic voltage only increased about 0.59%after 10 hours of electrolysis,in which indicates that NFRG-3 nanohybrids have excellent long-term stability.?2?Under the premise of complete exfoliation of NiFe-LDH,the assembly of LDH with other2D material?MoS₂?can avoid the aggregation of LDH itself,and the synergetic catalysis could be realized by the interface modulation of the heterointerfaces.The results of various characterizations show that exfoliation will increase the defects of NiFe-LDH;Secondly,the NiFe-LDH nanosheets stand vertically on the MoS₂ nanosheets.The e-NF/MoS₂-2nanohybrids with good crystallinity show the best OER performance,with an overpotential of276 mV at a current density of 10 mA cm^-2 and a Tafel slope of 85 mV dec^-1.Moreover,e-NF/MoS₂-2 nanohybrids also have a large electrochemically active areas?ECSA?and excellent long-term stability.?3?A series of nanocomposites of three-dimensional graphene network?3DGN?supported NiFe₂O₄ nanoparticles were prepared using polylactic acid?PLA?solid-phase exfoliated NiFe-LDH and subsequent hydrolysis and etching.The results of various characterizations show that PLA can achieve an exfoliation efficiency of 6 wt%of NiFe-LDH,and this kind of solid-phase exfoliation strategy is universal for LDH-based materials;The small molecule organic acid produced by the hydrolysis of PLA will etch the NiFe-LDH nanosheets and then transform them into NiFe₂O₄ nanoparticles,which can increase the number of active sites on the catalyst surface;NFO/3DGN-10 nanocomposites exhibit excellent OER activity with an overpotential of 272 mV at a current density of 10 mA cm^-2,and a small Tafel slope of 64 mV dec^-1.In addition,NFO/3DGN-10 nanocomposites also have a large electrochemically active areas?ECSA?and excellent long-term stability.