Study On The Preparation Of Cobalt/nickel Phosphide Nanosheets Based On Sodium Alginate And Its Electrolysis Of Water

With the progress of society,strong dependence on fossil fuels and serious environmental pollution are driving people to search for alternative sources of energy.Hydrogen is considered as an ideal clean and sustainable candidate to replace exhaustible fossil fuels.Hydrogen generation from water is a environmentally friendly and sustainable pathway,among many hydrogen production methods,so it has been widely studied.Electrocatalytic decomposition of water consists of two semi-reactions,namely hydrogen evolution reaction?HER?and oxygen evolution reaction?OER?.At present,the key is to find an efficient catalyst.Currently,noble metals?such as Pt,Ir?and their alloys are believed to be the most high-performance electrocatalysts.However,its high cost and scarcity limit its application.Transition metal phosphides?TMPs?have become a research hotspot of non-noble metal electrocatalysts due to their high activity and low cost.In addition,two-dimensional?2D?nanomaterials have become ideal catalysts because of their large specific surface area,abundant active sites and short distance electron/proton transport.Using sodium alginate?SA?as raw material,cobalt/nickel phosphide nanosheets were prepared by ice-templating,and they exhibited excellent electrocatalytic performance.?1?Firstly,SA was used as raw material to obtain cobalt aerogel precursors by using ice-templating.Then the precursors were oxidized at 400°C in air.Subsequently,CoP-400 nanosheets were prepared by phosphating at 350oC in Ar atmosphere.As a result,The obtained CoP-400 exhibit excellent HER performance at all pH values?0.5 M H₂SO₄,1 M KOH and 1 M PBS?,such as high current density,low Tafel slope and excellent stability.In order to reveal the catalytic mechanism,density functional theory?DFT?calculations were carried out in acid and alkaline conditions at different sites on the?011?facet of CoP to obtain the most favorable sites for HER.The results show that P-top and Co bridge are the active sites in acid and alkaline conditions,respectively.?2?SA was used as raw material to obtain nickel aerogel precursors by using ice-templating.Then the precursors were oxidized at 400°C in air.Subsequently,Ni₂P-400-350 nanosheets were prepared by phosphating at 350°C in Ar atmosphere.Ni₅P₄-500-350 nanosheets were prepared by oxidation at 500°C and phosphating at350°C.The obtained examples exhibit excellent HER performance at 1 M KOH.The results show that both of them have excellent catalytic performance,but the performance of Ni₅P₄-500-350 is better than that of Ni₂P-400-350.In addition,we also studied the effects of oxidation temperature and phosphating temperature on the products.?3?SA and reduced graphene oxide were used as raw materials to obtain Co/r-GO aerogel precursors by using ice-templating.Carbonization was then carried out at 600°C in Ar atmosphere.CoP-600/r-GO nanosheets were obtained by phosphating in Ar atmosphere.The OER performance were also studied under alkaline conditions?1 M KOH?,and the results show that CoP-600/r-GO has good electrocatalytic performance.