| Global primary energy consumption has unprecedented increased due to boost in population number.Annual global primary energy consumption has increased to 17.9 terawatts(TW)in 2017 and it is predicted as 22 TW by 2030.It undoubtedly warns that at the end of the current century,the global energy demand will have been multiplied.In this context,numerous efforts have been devoted to handle the grand challenge of 21st century with a clean,and sustainable approach.Molecular hydrogen is considered as a major energy carrier for the future world.The most desirable source is water,as it is abundant and contains no carbon.Water electrolysis is believed a reliable path to produce clean energy as it splits water molecule into hydrogen gas and oxygen gas.Water electrolysis requires efficient catalysts to proceed process effectively.Currently,precious metal based electrocatalysts are in common use owing to their high catalytic performance.But less reserves and higher cost of precious metals based electrocatalyst largely limits their large scale applications.In addition,it is generally observed that precious as well as non-precious metal based electrocatalysts start to lose activity under drastic conditions,thus exhibit insufficient activity and durability.Water electrolysis requires effective designs of electrocatalysts to overcome the associated issues such as high cost,insufficient activity and low durability under drastic environment.This dissertation demonstrates the design of electrocatalysts to perform water reduction and water oxidation efficiently along with prolonged durability at higher proton concentrations.The main findings are summarized as following:1.A design of precious metals free nanocomposite catalyst based on sandwich-type polyoxometalates(POMs)and cobalt diselenide nanobelts(CoSe2-NBs)was demonstrated to perform hydrogen evolution reaction at high proton concentrations.This design of nanocomposite catalyst demonstrated that effective coordination chemistry between CoSe2-NBs and POMs enable the stabilized POM to earn better advantage of their prestigious electron-proton reservoir-like properties to facilitate proton-coupled electron transfer(PCET)in order to generate molecular hydrogen efficiently at higher proton concentrations.2.The electrocatalytic oxygen evolution reaction(OER)at the anode is a slow reaction that requires an overpotential in substantial excess of its thermodynamic potential(1.23 V vs RHE,at standard temperature and pressure)to deliver an acceptable current density,e.g.,10 mA cm-2.In order to reduce the energy cost associated with sluggish kinetic of multiple electron process and O-O bond formation,development of unprecedented exfoliated ruthenium oxide nanosheets,RuO2-NSs,prepared via a facile hydrothermal method is demonstrated.Next,the as obtained RuO2-NSs were annealed in the presence of air to obtain ultrathin RuO2-nanostrips with average length and width of 10.6 nm and 4.8 nm,respectively.RuO2-nanostrips demonstrated remarkable water oxidation efficiency under acidic conditions with a small overpotential of 200 mV at 10 mA cm-2.The electrocatalytic water oxidation activity of RuO2-nanostrips was observed as superior to that of commercially available RuO2 and all other sheet-derived ruthenium oxide-based electrocatalysts reported to date for OER in acidic solution.The extraordinary OER activity was attributed to rich edges with coordinatively unsaturated sites of ultrathin RuO2-NStps.This research work,the demonstrates the design of nanocomposite catalysts to facilitate PCET for boosted electrocatalysis.In addition,exposing increased number of accessible active sites for electroactive species to attain extraordinary electrocatalytic activity is also well demonstrated in this work.This thesis work,offers new opportunities to design highly efficient and durable electrocatalysts to perform HER and OER at higher proton concentrations. |
