Preparation Of Nickel-iron Layered Double Hydroxide/Nickel Foam Composites And Its Electrocatalytic Performance

In recent years,the overexploitation of fossil fuels has led to a rapid decline in global energy reserves,while causing a series of environmental problems.Here,hydrogen energy is highly expected as a safe,reliable and sustainable secondary clean energy source.It is recognized as the most promising green means of hydrogen production because it is free from dependence on fossil fuels,and the product is pure and rate controllable.Currently,most of the commercial catalytic materials for water electrolysis are precious metals such as ruthenium and iridium,which severely limit the large-scale application of water electrolysis technology due to their high prices and low reserves.Therefore,the development of stable,efficient and low-cost non-precious metal catalysts is a key issue to be addressed in this technology.Nickel-iron layered double hydroxide（NiFe-LDH）,the most efficient OER catalyst in alkaline environment,was selected as the target of this study.The self-supported NiFe-LDH/NF composite was produced by a one-step hydrothermal method,with nickel foam as the collector and NiFe-LDH nanosheets growing uniformly on the NF substrate,cleverly solving the main problems of NiFe-LDH as a catalytic electrode material,such as lamellar block stacking,poor electrical conductivity and poor bonding stability,and further improving its catalytic performance.The details of this paper are as follows:1.The composites were characterized for different hydrothermal synthesis times,and the preferred synthesis time was 12 hours.the sample 12-Ni₂Fe₁-LDH/NF just required an ultra-low overpotential of 274 m V to reach a current density of100 m A cm^-2in the OER test.In addition,the NiFe-based composites produced by the one-step hydrothermal method have superior OER catalytic performance compared to Ni₂Fe₁-LDH and commercial Ru O₂electrode materials produced by other composite methods.2.Adjustment of the iron salt doping indirectly modulates the growth morphology and crystal electronic structure of NiFe-LDH nanosheets,further optimising the catalytic performance of the composites.At an appropriate Ni-Fe ratio（2:1）,the Ni₂Fe₁³⁺-LDH/NF samples produced with high-valent iron salts(Fe³⁺)initiated an"adaptive"electrochemical reconstruction during the OER process,resulting in a stable protective barrier（Ni OOH-containing rough layer）on the surface of the flakes,which enabled the catalyst activity and stability to be optimised simultaneously.In the OER test,the sample showed an overpotential value as low as 265 m V at a current density of 100 m A cm^-2and a very low Tafel slope of24.77 m V dec^-1.It also requires an ultra-low potential of only1.61 V during full hydrolysis and remains stable over 80 h of CP testing,which provides a good practical application.