Highly Efficient And Stable Bistratal Non-noble Metal Catalysts For Overall Solar Water Splitting

To achieve sustainable production of H2 fuel through water splitting,low-cost,high-efficient and stable electrocatalysts for the hydrogen-evolution reaction(HER)and the oxygen-evolution reaction(OER)are required to replace precious Pt and IrO2 catalysts.To this end,we prepared double-layered catalysts of non-precious metal phosphates and sulfides on nickel foam by simple electrodeposition method.When the prepared electrodes are connected with the solar cell in series,efficient and stable water decomposition driven by solar energy is realized.We mainly carried out the following two aspects in this thesis.(1)We developed an efficient,stable and bifunctional Ni-Co-S/Ni-Co-P bistratal electrocatalyst on Ni foam(NF)using simple electrodeposition methods.The efficient contact on Ni-Co-P/NF interface along with the porous NiCo-S surface results in superior electrocatalytic activity in basic solution for both OER and HER.Only-0.11 V vs.RHE is required at a current density of-20 mA/cm2 for HER and 1.47 V vs.RHE at 50 mA/cm2 for OER,significantly outperforming bare Ni-Co-S or No-Co-P on NF.Most crucially,when functioning as a bifunctional catalyst for overall water splitting,a small cell potential of 1.49 V can drive 10 mA/cm2 which can sustain for more than two days.Subsequently,10.8%-efficient overall solar water splitting was achieved when driven by three ordinary Si solar cells.Such bistratal structure is expected to provide a new platform for the design of highly efficient,low-cost and durable catalysts for water electrolysis systems.(2)On the basis of the first work,we try to improve HER performance using Ni-Mo-S.Ni-Co-P/NF interface remains to keep the efficient contact of Ni-Co-P/NF interface,and a similar electrodeposition method is used to deposite a Ni-Mo-S layer on the Ni-Co-P/NF surface.This double-layered catalyst achieves a high-efficient electrocatalytic activity of HER.At-10 mA/cm2,only an overpotential of 0.036 V vs.RHE is required.In addition to the high catalytic activity for HER of Ni-Mo-S,the effective contact between Ni-Co-P/NF and the porous Ni-Mo-S surface accelerates the charge transfer from the electrode to the electrolyte,leading to the superior HER performance.When using Ni-Mo-S/Ni-Co-P/NF as a cathode and Ni-Co-S/Ni-Co-P/NF as an anode for the overall water decomposition,only 1.45 V is needed to obtain the current density of 10 mA/cm2.Finally,when the electrocatalytic cell was powered by three Si solar cells,13.8%-efficient overall solar water-splitting was achieved.