Preparation And Electrocatalytic Performance Of Supported Cobalt-Based Catalysts

Energy crisis issues based on traditional fossil fuels have attracted great attention due to the increasing economical development and environmental concerns.It is imperative to look for clean,efficient and sustainable alternate energy sources,which is an effective way to address energy crisis and alleviate environmental pollution.Hydrogen energy,as a clean fuel with zero carbon emission,has the advantages of high energy density and no pollution of combustion products,so it is considered as a significant green energy.Electrochemical water splitting driven by renewable energy sources is a promising approach for environmentally friendly production of high-purity hydrogen fuels.It has been widely considered to be a "core clean energy technology" that is essential for the hydrogen economy.However,it is necessary to overcome the activation barrier of two half-cell reactions.Therefore,the effective electrocatalysts must be implemented to minimize the overpotentials.Co-based alloy materials as earth-abundant functional materials with remarkable catalytic performance have attracted a great interest in catalysis.The primary ideas of this paper are to prepare Co-based catalysts by simple electroless deposition and to evaluate their electrolytic water activity.The main results include the following aspects:?1?The Co-Cu-P/NF alloy catalysts were successfully loaded on the nickel foam?NF?substrates by facile electroless deposition and the oxygen evolution reaction?OER?activity of the catalysts was investigated.It was found that the preparation conditions of Co-Cu-P/NF alloy catalysts and the annealing treatment at high temperature had an effect on the OER performance of the catalysts.The Co-Cu-P/NF catalysts electroless deposited for 10 min with annealed at 300? exhibit the best electrolytic water property.The overpotential of the catalysts is 307 mV at a current density of 10 mA·cm^-2 and the Tafel slope is 71.76 mV·dec^-1,which indicates a rapid reaction kinetics.After annealing at 300?,the Co-Cu-P/NF catalysts show excellent stability and strong interface bonding ability.The stability test for 85000 s is carried out at a constant current density of 10 mA·cm^-2 and the morphology is maintained.In addition,Co-Cu-P/NF catalysts have significant catalytic activity for hydrogen evolution reaction?HER?as well and only need a HER overpotential of 158 mV in 1.0M KOH electrolyte and the Tafel slope is 81.2 mV·dec^-1,indicating that the Co-Cu-P/NF catalysts possess favorable HER property.?2?High performance Fe-Co-P alloy catalysts were deposited on porous NF using electroless deposition method.With Fe incorporation,the OER activity of the catalysts has been greatly improved.The Fe-Co-P/NF alloy catalysts electroless deposited for 5min with 5/5 Fe²⁺/Co²⁺ concentration ratios in electroless bath own the best OER catalytic activity towards water splitting.The resultant Fe-Co-P/NF catalysts yield extraordinary OER performance with an overpotential as low as 250 mV at 10mA·cm^-2,a small Tafel slope of 49.2 mV·dec^-1,and excellent OER stability.At the same time,Fe-Co-P/NF catalysts also exhibit fine HER performance with 163 mV overpotential.Utilizing Fe-Co-P/NF as both the anode and the cathode for overall water splitting,a current density of 10 mA·cm^-2 is achieved at a cell voltage of as low as 1.68 V vs.RHE with excellent stability.It means that Fe-Co-P/NF alloy can be used as a highly efficient bifunctional electrocatalysts for overall water splitting.?3?Graphene?Gr?quantum dots exhibit advantages of large specific surface area,rapid electron mobility and abundant catalytic sites.Moreover,Gr/transition metal composite can effectively enlarge the specific surface area of single transition metal materials and increase the conductivity of the materials,achieving outstanding catalytic performance and stability of electrochemical water splitting.The co-deposition of Gr quantum dots with Fe-Co-P alloy on NF substrates was achieved by adding GO quantum dots into Fe-Co-P bath.The Fe-Co-P-Gr/NF composite catalysts were successfully synthesized using electroless composite deposition method.The OER activity towards water splitting of Fe-Co-P-Gr/NF catalysts with different volumes of Gr quantum dots was investigated.The catalysts electroless deposited for 2min with 800?L GO quantum dots show extraordinary OER catalytic activity in alkaline media.The Fe-Co-P-Gr/NF catalysts are capable of yielding a current density of 10 mA·cm^-2 at an overpotential of only 230 mV,which is 20 mV lower than that of Fe-Co-P/NF catalysts.The decrease of Tafel slope from 49.2 mV·dec^-1 to 37.9mV?dec^-1 indicates that Fe-Co-P-Gr/NF catalysts possess a faster reaction kinetics.Functioning as the bifunctional catalyst,Fe-Co-P-Gr/NF catalysts could deliver a current density of 10 mA·cm^-2 with a cell voltage of 1.58 V vs.RHE in a two-electrode electrolyzer,which is superior to Fe-Co-P/NF?1.68 V vs.RHE?.The overpotential of composite plating Fe-Co-P-Gr/NF catalysts is reduced by 100 mV,which indicates that the electroless composite Fe-Co-P-Gr/NF catalysts are more in line with the practical application standard.