Study On Electrocatalytic Performance On Water Splitting Of Self-Supported Transition Metals-Based Amorphous Alloy

The impact of energy crises and environmental pollution has urged the development and application of hydrogen energy.Compared with other technologies,the electrochemical water splitting driven by intermittent solar,wind,and tidal energy sources is regarded as the most promising approach to produce high-purity hydrogen.However,the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)in water splitting involve multiple electron transfer and the absorption and desorption of intermediate substances,which is kinetically not favored.Therefore,the design of the efficient and low-cost catalyst is of great significance for saving the cost of hydrogen production by electrolyzing water and improving energy conversion efficiency.In recent years,transition metal-based amorphous alloys,such as iron-based,nickel-based,and cobalt-based alloy nanoparticles,films,and ribbons have been proven to exhibit good electrocatalytic performance due to more reactive sites and corrosion resistance.Among them,the amorphous alloy ribbons have the advantages of self-supporting,simpler electrode preparation process and good electrochemical stability,and which is regarded as the promising electrocatalyst.This paper takes transition metal-based amorphous alloys as the research object,and aims to obtain highly efficient and stable electrocatalytic materials through composition design and process control.Besides,the morphology,structure,composition and electrochemical properties of the ribbon were characterized.This paper mainly studies the following contents:Firstly,taking FeMo PC amorphous alloy as the research object,the microstructure and surface chemical state of amorphous alloys obtained by different process treatments were characterized,and the influence of process treatments on catalytic activity and stability was analyzed.It is found that the catalytic activity and stability of Fe₇₆Mo₄P₁₃C₇ amorphous alloy ribbons are significantly improved by the two-step electrochemical cyclic voltammetry-dealloying treatment,which is mainly due to its unique nano-island/amorphous matrix sandwich structure.The surface nano-island structure not only provides abundant active sites but also contains Mo and acid-resistant metal phosphates,which can effectively prevent the internal matrix from being continuously degraded during the HER process.The FeMo PC metal framework as the matrix promotes charge transfer and effectively accelerates HER process.Secondly,taking FeCoMo PC amorphous alloy as the research object,the nanoporous/amorphous layer composite structure was obtained by electrochemical dealloying treatment.The HER and OER performance of the catalyst in 1.0 M KOH solution was tested,and the catalytic performance of Mo doping was studied.It is found that Mo doping changes the electronic structure of the alloy,reduces the number ratio of Fe^?+and Co^?+,and moves the higher binding energy of Fe and Co,which adjusts the adsorption of OH^-by the active site.Based on this,Mo doping is good for OER but not good for HER.The prepared De-(Fe_0.5Co_0.5)₇₅Mo₅P₁₃C₇ exhibits excellent bifunctional catalytic properties,with a low water splitting voltage of 1.617 V at 10 m A cm^-2 and excellent durability for 36 h.In the long-term electrolysis water reaction process,the surface layer of De-(Fe_0.5Co_0.5)₇₅Mo₅P₁₃C₇ is derived to have a large specific surface area and a well-developed pore structure,exposing multiple active sites,and the porous channels accelerate the electron transport under the synergistic effect of the amorphous matrix.The appropriate amount of Mo doping improves the adsorption of the catalyst to the reactive species,thereby increasing the intrinsic OER activity of the catalyst.Thirdly,taking Fe(Co,Ni)PC amorphous alloy as the research object,the catalytic activity of the catalyst was further improved through electrochemical dealloying.The OER catalytic performance of the catalyst in 1.0 M KOH was tested,and clarify the reasons for the difference in catalytic performance due to different doping elements.It is found that Fe₂₇Co₂₇Ni₂₇P₁₃C₆(De-Fe Co Ni PC)after electrochemical dealloying has the best catalytic activity and stability.At a current density of 10 m A cm^-2,its OER overpotential is only 241 m V,and during the stability test,there is almost no degradation in performance.The results show that the doping of Co and Ni reduces the charge density around the alloy atoms and promotes the formation of transition metal phosphates as active materials.The phosphates and various metal oxides or oxyhydroxides with various valence states optimize the adsorption energy of the active site to the intermediate.The strong charge transfer between Fe,Co,Ni and P also effectively accelerate the kinetics of the reaction.Besides,the nanoporous structure obtained after dealloying not only exposes abundant active sites,but also facilitates material transport.Thus,De-Fe Co Ni PC exhibits high catalytic activity.