Cobalt-based Electrocatalysts And NiMoN Compounds With Excellent Electrocatalytic Activity For Water Splitting

With the rapid increase of world population,modern society needs more and more energy.Fossil fuels are the mostly used energy nowadays.However,fossil fuels are doomed to run out in the near future and the overuse of fossil fuels has caused many environment issues.So,it is vital to find some kind of renewable and clean energy.Hydrogen is widely thought as the promising energy to replace fossil fuels for its high heat value and broad resources,and it is also environment friendly.Among the various methods of producing hydrogen,electrochemical water splitting has caught much attention just because it can get pure hydrogen with nothing else harmful produced.For now,the compounds of noble-metal remain the best of many electrocatalysts.The high price and lack of abundance limit their application in industrial production.To synthesize transition-metal compounds that are abundant on earth to replace noble-metal catalysts is becoming one of the research hotspots.The main contents of this article are as follows:(1)Versatile cobalt-phosphorus(Co-P)precursor was synthesized on Ni foam(NF)with an electrodeposition method.Simple room-temperature treatment of the precursor with 1 M NaOH and 0.5 M H2SO4 allows for the production of cobalt oxide nanosheets(CoxOy/NF)and cobalt phosphate/phosphide(Co-Pi/CoP/NF),respectively.The resulting CoxOy/NF shows a low overpotential(η10)of 80 mV at-10 mA/cm2 in alkaline electrolyte(pH =14)for hydrogen evolution reaction(HER)toward electrocatalytic water splitting.The Co-Pi/CoP/NF exhibits a low η10 of 112 mV in acidic electrolyte(pH=0),in which the synergy between Co(+2)and Co(+3)may play an important role in the reaction.(2)Nickle-Molybdenum-Oxygen precursor is successfully synthesized through a hydrothermal method.After nitridation at different temperatures,Nickle-Molybdenum based nitrides:NiMoN-500,NiMoN-600,NiMoN-700 and NiMoN-800 are obtained.This series of nitrides all show catalytic activity for both hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).For OER,NiMoN-700 just needs an overpotential of 210 mV at a current density of 10 mA/cm2 which makes it a highly-efficient electrocatalyst for OER.Good conductivity and large electrochemical surface area are the main reasons for its excellent catalytic performance.And the synthetic effect of double metal active sites exposed also plays an important role during the OER process.