Nanocomposite Template-derived Transition Metal Catalyst As Active Electrocatalyst For Water Splitting

Hydrogen,as a sustainable and green fuel with high energy density,has been proposed as an ideal energy production to replace fossil fuels in the future.Electrochemical water splitting powered by renewable electricity is one of the most attractive methods for high purity hydrogen production.However,efficient water splitting is largely dependent on highly efficient and robust electrocatalysts that can sufficiently overcome the sluggish kinetics of the two half reactions,namely the hydrogen evolution reaction(HER)and the oxygen evolution reaction(OER).Currently,precious metal and noble metallic oxide(such as Pt,RuO2 and IrO2)have been perceived as the most efficient catalysts for HER and OER.However,the high cost and low earth abundance of these noble metals present barriers for their wide-spread deployment.Therefore,the preparation of high-efficiency and low-priced non-noble metal catalysts is vital for the large-scale water splitting industrial and commercialization of these novel energy conversion devices.To enhance catalytic activity,structuring the catalysts with hollow and porous fabric would be a valid way to enhance specific surface and expose active sites to the electrolyte.Therefore,we design of a series of Prussian blue analogues(PBAs)and layered doulble metal hydroxides(LDHs)with various chemical composition and structure as templates to fabricate a series of transition metal-based electrocatalyst with hollow and porous structures.Despite all this,the poor electrical conductivity between electrocatalyst and the electrode base is disadvantageous for the electrocatalytic process.Hence,the formation of three-dimensional hybrid structures between the electrocatalyst nano-particles and a conductive based could effectively exert their synergistic effect to further improve their catalytic performance.The details are listed as following:1.The penroseite(Ni,Co)Se2 nanocages anchored on 3D graphene aerogel(GA)was synthesized from NiCo PBA precursor and further their applications in water splitting electrocatalysis.The unique morphology of nanocages provides more exposed active sites,whereas direct contact between(Ni,Co)Se2 and reduced graphene oxide(rGO)nanosheets promotes the electron transfer.As a result,the(Ni,Co)Se2-GA hybrid catalyst shows stable performance toward both the OER and HER that is superior to that of most non-noble metal-based electrocatalysts reported so far.More importantly,the(Ni,Co)Se2-GA can also efficiently catalyze the overall water splitting with a low voltage of 1.6 V at 10 mA cm-2 and outstanding durability.2.The MnxCo1-xP nanocubes anchored on reduced graphene oxide(rGO)was synthesized from MnCo PBA precursor and further investigated their applications in water splitting electrocatalysis.The Mn and Co concentration in MnxCo1-xP can be facilely controlled through adjusting the molar ratios of MnCo PBA precursor.The OER and HER performance of MnxCo1-xP-rGO could be enhanced when manganese content is increased.As a result the Mn0.6Co0.4P-rGO hybrid catalyst exhibit superior catalytic activities and stable performance towards both the OER and HER.Not only that,the Mn0.6Co0.4P-rGO act as both cathode and anode in an electrolytic cell which show an excellent performance in water splitting with a low voltage of 1.55 V at 10 mA cm-2 and remarkable durability.3.The hollow MnCo-P nanowire arrays directly grow on electrode was synthesized from MnCo LDH nanowire arrays precursor and further their applications as a bifunctional catalysts for urea oxidation and hydrogen evolution towards more efficient electrolytic hydrogen generation.The hollow MnCo-P nanowire arrays directly grow on carbon paper(MnCo-P/CP)behave as a highly active durable 3D catalyst electrode for the urea oxidation reaction(UOR)with the required potential of 1.29 V vs.RHE to drive an abnode current density of 10 mA cm-2 in a 1.0 mol L-1 KOH with 0.5 mol L-1 urea.Remarkably,the MnCo-P/CP shows excellent performance toward the HER which enables it to be a bifunctional catalyst for both the UOR and HER towards energy-saving electrochemical hydrogen production.The corresponding two-electrode electrolyzer using MnCo-P/C as both the cathode for HER and the anode for UOR only needs a cell voltage of 1.23 V to achieve a current density of 10 mA cm-2 1.0 mol L-1 KOH with 0.5 mol L-1 urea,which is 340 mV less than that for conventional water splitting.