Preparation Of Iron Foam Self-supporting Electrocatalsts And Their Performances For Water Splitting In Neutral Medium

In view of the increasingly deteriorating energy shortage and environmental pollution,it is urgent to develop renewable and clean energy sources that can replace traditional fossil fuels.As an ideal energy carrier,hydrogen（H₂）has attracted wide attention due to its high energy density(～142 MJ kg^-1),net-zero carbon and recyclable combustion products.Production of hydrogen through electrocatalytic water splitting powered by electric energy is a promising strategy for the hydrogen economy in the future.And it can also be combined with intermittent energy sources such as wind and solar energy to improve the utilization efficiency of the entire renewable energy.Therefore,electrocatalytic water splitting has attracted tremendous attentions and has been growing rapidly with the concerted efforts of the researchers in the world.In fact,electrocatalytic water splitting consists of two half reactions:hydrogen evolution reaction（HER）at the cathode and oxygen evolution reaction（OER）at the anode.However,the slow kinetics of the HER and OER severely limit water splitting due to the complex transfer pathway of multi-proton coupled electrons.At present,commercial electrolytic cells include acidic proton exchange membrane electrolyzers and alkaline water electrolyzers.Unfortunately,the popular electrocatalysts of proton exchange membrane electrolyzers are precious metals（Pt,Ir,Ru）,which would increase costs and limit its widespread application.Moreover,the alkaline water electrolyzers can only operate at low current density when applying non-noble metal electrodes,which would result in low energy conversion rate.What’s worse,strong acidic or alkaline solution is a highly corrosive environment,which would lead to acid mist pollution,resulting in serious corrosion problems of catalyst and electrolytic cell.To avoid problems with proton exchange membrane electrolyzers and alkaline water electrolyzers,electrocatalytic water splitting can be performed in neutral and near-neutral conditions.In this paper,we synthesized a series of self-supporting catalytic materials on iron foam at room temperature and explored their electrocatalytic water splitting activity in neutral medium.The main contents of this paper are as follows:（1）The Co-doped Fe OOH nanomaterials（IF-Co-6）are grown directly on the iron foam substrate by corrosion engineering at room temperature.The obtained IF-Co-6 catalyst demonstrates superior electrocatalytic performances for OER,with an extremely low overpotential of around 429 m V at 10 m A cm^-2 and Tafel slope of 111.8 m V dec^-1 in neutral medium.Moreover,the catalytic activity of IF-Co-6 could be retained for 50 h under an overpotential of 500 m V with negligible attenuation,which revealed that IF-Co-6 possessed the robust stability for OER.（2）Iron doped nickel sulfide nanomaterials supported on iron foam were prepared at room temperature.Due to its three-dimensional sphere-like nanostructure,enhanced conductivity and abundant active sites,the as-prepared materials exhibit excellent HER activity in neutral medium.Therefore,a low overpotential of only 183 m V at current density of 10 m A cm^-2 and a Tafel slope of 130.9 m V dec^-1 are achieved on the catalyst obtained by adding 50 m M sodium sulfide for 2hours at room temperature.In addition,the current density of the catalyst did not significantly decay during the 12 h stability test.The above results fully demonstrate the potential of this material as a highly efficient HER electrocatalyst.