With the energy crisis and global warming,exploration of novel energy sources to replace fossil fuels is a hot topic.H2 is considered as an eco-friendly energy carrier due to its high energy density per unit mass,and ...With the energy crisis and global warming,exploration of novel energy sources to replace fossil fuels is a hot topic.H2 is considered as an eco-friendly energy carrier due to its high energy density per unit mass,and when consumed in engines or fuel cells,it produces only water as the byproduct.Conventional approach to H2 synthesis strongly depends on fossil fuels by steam reforming process,leading to serious CO2 emission.Nowadays,an eco-friendly alternative to produce H2 on a large scale is via electrochemical water splitting[1–7].The overall water splitting reaction consists of two half-reactions:the cathodic hydrogen evolution reaction(HER)and anodic oxygen evolution reaction(OER),both of which require catalysts to improve their efficiency and reduce their overpotentials[8].Although the state-of-the-art catalysts of Pt/C and IrO2/RuO2 exhibit high performance for HER and OER,their widespread uses are hindered by their scarcity and high cost.Moreover,using a bifunctional HER and OER electrocatalyst has advantages of simplifying the system and lowering the cost.As such,it is highly attractive to design and develop earth-abundant bifunctional water-splitting electrocatalysts.Transition-metal phosphides are an important class of compounds formed by the alloying of metals and phosphorus,and their good electrical conductivity is of great benefit to enhanced electrochemical performances[9–12].Recently,Fu’s group from Heilongjiang University have prepared NiCoP nanosheets grown on N-doped carbon coated Ni foam(NiCoP/NF@NC)[13].The linear sweeping voltammetry(LSV)curves show that the NiCoP/NF@NC electrode requires overpotentials of 31.8 mV for the HER and 308.2 mV for the OER to achieve 10 mA/cm^2 in 1.0 M KOH.The HER overpotential is much lower than those for NiP/NF@NC(126.6 mV)and CoP/NF@NC(112.1 mV),demonstrating NiCoP/NF@NC is superior in HER performance to CoP/NF@NC and NiP/NF@NC due to the synergistic effect.Moreover,for the OER catalysis,the overpotential of NiCoP/NF@NC electrode is also lower than those for NiP/NF@NC(349.1 mV)and CoP/NF@NC(383.3 mV).Notably,NiCoP/NF@NC has excellent long-term stability without obvious attenuation of performance after 10000 time cycles.Such 3D catalyst electrode has the following advantages for water splitting:(1)it acts as a bifunctional HER and OER electrocatalyst;(2)Ni foam accelerates the diffusion of ions and improve the electrocatalytic performance;(3)introduction of N-doped carbon nanostructures enhances the electrical conductivity and facilitates the transfer rate of electron.展开更多
文摘With the energy crisis and global warming,exploration of novel energy sources to replace fossil fuels is a hot topic.H2 is considered as an eco-friendly energy carrier due to its high energy density per unit mass,and when consumed in engines or fuel cells,it produces only water as the byproduct.Conventional approach to H2 synthesis strongly depends on fossil fuels by steam reforming process,leading to serious CO2 emission.Nowadays,an eco-friendly alternative to produce H2 on a large scale is via electrochemical water splitting[1–7].The overall water splitting reaction consists of two half-reactions:the cathodic hydrogen evolution reaction(HER)and anodic oxygen evolution reaction(OER),both of which require catalysts to improve their efficiency and reduce their overpotentials[8].Although the state-of-the-art catalysts of Pt/C and IrO2/RuO2 exhibit high performance for HER and OER,their widespread uses are hindered by their scarcity and high cost.Moreover,using a bifunctional HER and OER electrocatalyst has advantages of simplifying the system and lowering the cost.As such,it is highly attractive to design and develop earth-abundant bifunctional water-splitting electrocatalysts.Transition-metal phosphides are an important class of compounds formed by the alloying of metals and phosphorus,and their good electrical conductivity is of great benefit to enhanced electrochemical performances[9–12].Recently,Fu’s group from Heilongjiang University have prepared NiCoP nanosheets grown on N-doped carbon coated Ni foam(NiCoP/NF@NC)[13].The linear sweeping voltammetry(LSV)curves show that the NiCoP/NF@NC electrode requires overpotentials of 31.8 mV for the HER and 308.2 mV for the OER to achieve 10 mA/cm^2 in 1.0 M KOH.The HER overpotential is much lower than those for NiP/NF@NC(126.6 mV)and CoP/NF@NC(112.1 mV),demonstrating NiCoP/NF@NC is superior in HER performance to CoP/NF@NC and NiP/NF@NC due to the synergistic effect.Moreover,for the OER catalysis,the overpotential of NiCoP/NF@NC electrode is also lower than those for NiP/NF@NC(349.1 mV)and CoP/NF@NC(383.3 mV).Notably,NiCoP/NF@NC has excellent long-term stability without obvious attenuation of performance after 10000 time cycles.Such 3D catalyst electrode has the following advantages for water splitting:(1)it acts as a bifunctional HER and OER electrocatalyst;(2)Ni foam accelerates the diffusion of ions and improve the electrocatalytic performance;(3)introduction of N-doped carbon nanostructures enhances the electrical conductivity and facilitates the transfer rate of electron.
