Preparation Of Three-dimensional Graphene/NI Based Alloy Composite Electrode And Its Electrocatalytic Hydrogen Production Performance

Hydrogen is a kind of new energy with high calorific value,renewability and environmental friendliness,which can be alternative to the present industrial fossil fuels.Electrolysis of water in alkaline electrolytes has the advantages of mature technologies and high purity,but the large power consumption prevent the industrial production.The development of efficient hydrogen production catalyst for reducing the hydrogen evolution reaction overpotential is becoming a hot spot of current research.Though Pt-based metal catalyst can significantly reduce production potential,it cannot meet the needs of industrial production because of high cost,natural scarcity and the catalyst poisoning phenomenon.The transition metal Ni and Ni-based alloy with the relatively high catalytic activity and cheap cost can replace Pt catalyst for catalytic hydrogen evolution reaction,but it still has a large overpotential.Though nanoporous Ni-based alloys have low overpotential in hydrogen evolution reaction,the high chemical activity lead to a poor stability.In spite of the superior specific surface area,high conductivity and electrochemical stability,the catalytic activity of three-dimensional graphene in hydrogen evolution reaction is poor,which can be effectively reduced the overpotential by the transition metal atom doping.In this study,nanoporous Ni-based alloys were used as substrates by CVD method,which were formed on the basis of different alloys.The three-dimensional grapheme/Ni-based alloy composites have superior specific surface area,high conductivity and electrochemical stability,which can significantly reduce the overpotential.The main contents of this study are as follows:(1)Different Ni-based alloys were prepared based on the alloy phase diagram.The XRD analysis shows that the homogeneous NiCuMn and NiCoMn alloys belong to face-centered cubic single-phase solid solution,which are beneficial to the formation of three-dimensional nanoporous structure with uniform pore sizes distribution.Nano-porous Ni-based alloys were successfully prepared by de-alloying method.The BET and TEM analysis shows that the pore sizes of nanoporous NiCo alloys are distributed in 3?6 nm.(2)The electrocatalytic hydrogen production performance of different nanoporous Ni-based composites were investigated that nanoporous Ni-based alloy with low overpotential and Tafel slope has a poor electrochemical stability.(3)Three-dimensional graphene/Ni-based alloy composites were successfully prepared by CVD method,which are used nano-porous NiCo alloys as substrates.NiCo-doped three-dimensional graphene was formed by chemical etching.Extending the growth time and improving the growth temperature can enlarge the aperture of three-dimensional graphene/NiCo composites and NiCo doped three-dimensional graphene,with the overpotential increased at the same time.NiCo doped three-dimensional graphene with a superior conductivity and excellent electrochemical stability has the smallest pore size(100-300 nm),the lowest overpotential(175 mV at a current density of 20 mA/cm~2)and the lowest Tafel slope(72 mV/dec)when grows at 800? for 1 minute,which can be expected to replace Pt as a ideal hydrogen production electrode material.