Structure Control And （Photo） Electrocatalytic Activity Of Phosphate And TiO₂-based Nanoarrays

As the most ideal clean energy carrier,the development of hydrogen energy provides an effective way to solve the current increasingly serious energy crisis and environmental problems.Transition metal phosphide and TiO₂-based nanoarrays have large specific surface area,more catalytic active sites and fast charge transport capacity.Therefore,they have great potential for development in the field of（photo）electrocatalytic water splitting.Aiming at some problems of（photo）electrocatalytic materials such as high overpotential,limited light absorption and high cost,the electrocatalytic performances of non-noble metal electrocatalyst like transition metal phosphide and the photoelectrocatalytic performances of TiO₂-based nanoarrays are studied systematically and deeply in this paper.The details are as follows:The first part focuses on the preparation,structure control and electrocatalytic performances of transition metal phosphide electrodes.We synthesize a series of Ni_XCo_1-XP nanostructures（X=0-1）with adjustable structure and composition,and the electrocatalytic performances were modified by cyclic voltammetric（CV）sweeping.It was found that the composition and crystallinity of the samples did not change after CV sweeping,but the surface of the samples became rough after CV sweeping,and a large amount of nanoparticles were formed on the surface,which increased the specific surface area,catalytic activity site and active/electrolyte interface,reduced the interface electron conduction resistance,and improved the electrocatalytic hydrogen evolution performances.Among them,in the acidic system,the hydrogen evolution potentialη₁₀（overpotential at 10mA/cm²）of CoP nanowire/titanium electrode（4000 cycles sweeping）is 39mV;In the alkaline system,the hydrogen evolution potential η₁₀of Ni₂P nanoplates/Ni foam electrode（3000 cycles sweeping）is 49.3mV,and the hydrogen evolution potential η₁₀of NiCoP nanowire/Ni foam electrode（4000 cycles sweeping）is 43mV,which are superior in the same material systems.In addition,via adjusting the CV sweeping parameters of NiCoP nanowire/Ni foam electrode,combined with the corresponding electrochemical behaviors,microstructure and performance analysis,we proposed a surface roughening enhanced electrocatalytic hydrogen evolution mechanism model.The second part mainly focuses on the structural control and photoelectrocatalytic water splitting performances of the TiO₂-based nanoarray photoanode.Using electrochemical deposition method to deposit visible light capture agent BiVO₄ on the surface of TiO₂nanorods,meanwhile the thickness of BiVO₄ was optimized by changing the deposited coulombic quantity of BiVO₄.On this basis,the co-catalyst Co-Pi was further photodeposited to prepare TiO₂/BiVO₄/Co-Pi electrode with a photocurrent density of 1.86mA/cm²(1.0V_RHE),which was about 1.2 times of TiO₂/Bi VO₄.The incident photoelectric conversion efficiency（IPCE）is about 26%（450nm）,and the hydrogen evolution rate is about 7.31μmol/cm²/h.Further analysis shows that TiO₂/BiVO₄ forms the"Ⅱ"energy level scheduling,provided an excellent heterogeneous interface for the transmission and separation of photogenerated charge.At the same time,combined with the electron transport channel role of one-dimensional TiO₂ nanorods and the hole transport medium role of co-catalysts,it greatly reduces the carrier recombination efficiency and photoelectrocatalytic water splitting reaction barrier,thereby improves the photoelectrocatalytic water splitting performances.