Preparation Of Metal Oxide Nanorods And Enhancement Of The Performance Of Photoelectrochemical Water Splitting

In this century,the over-exploitation of fossil fuels and fossil energy has led to a series of energy crises and environmental problems.For the rapid and sustainable development of society,there is an urgent need to develop a new green and non-polluting energy source to replace traditional fossil fuels.As an emerging energy source,hydrogen energy has many advantages such as being clean,efficient,safe,storable and transportable;it is considered to be the most ideal pollution-free green energy source in the new century.Photocatalytic decomposition of water for hydrogen production is an effective method to produce hydrogen using solar energy,which is considered to be able to alleviate the current energy crisis.However,the current low efficiency of photocatalysis is expected to improve the efficiency of catalytic hydrogen production by combining with electrocatalysis and using an applied bias to promote the separation of photogenerated electron-hole pairs.Among many photoelectcatalytic materials,metal oxides are one of the most researched materials for improving photocatalytic efficiency due to their stability,non-toxicity,affordability,and abundance in the crust;this paper is a performance study on the preparation of ordered nanorod arrays of two materials,α-Fe₂O₃ and Ti O₂,as photoanodes for efficient photocatalytic decomposition of water.The main research capabilities are as follows.（1）The ordered Ti O₂ nanorod arrays were successfully prepared by hydrothermal method,with the arrays perpendicular to the substrate surface,30-50 nm in diameter,and about 380μm in length.The nanorods were also modified by F doping,and the F doped into titanium oxide formed new compounds with Ti,and O,improved the photocatalytic performance of the material.The results show that 0.05F-T has the most excellent performance,with the maximum photocurrent of 7.34m A/cm² for the linear scan at a bias of 1.8 V vs.RHE,which is 4.61 times higher than that of 1.59m A/cm² for simple titanium rods,and the photocurrent density of 0.05F-T is maintained at 6.99m A/cm² at a bias of 1.23 V vs.RHE,which is only attenuated by 0.05%.The timing current curve data indicate that the stability of the resulting materials are all good.In the wavelength range of 325nm-375 nm,the F-doped titanium oxide nanorods exhibited a very significant photocurrent response,much higher than that of the undoped samples,with the largest photocurrent density of 0.05 F-T.In addition,the F doping broadens the absorption edge of Ti O₂ from 425 nm to the visible region,and,with the increase of bias voltage,the visible response is gradually obvious.Finally,the photocatalytic decomposition of aquatic hydrogen by 0.05F-T was found to have the best performance by the photoelectron-coupled hydrogen production test,which reached a hydrogen production of 836.95μmol/cm² under UV-Vis illumination for 5 h at a bias voltage of 1.8 V vs.RHE,which was 6.71times higher than that of Ti O₂（124.71μmol/cm²）.（2）An efficient photoelectrocatalytic photoanode material Pd@Ti O₂ was obtained by reducing Pd²⁺in solution to metal Pd using the photogenerated electron holes of titanium dioxide itself,and Pd was loaded in situ on the surface of the material to form a uniform layer of very thin monolithic palladium.The surface loading of Pd on Ti O₂ was determined by various test characterizations,and it was also found that the loading of Pd did not change the original material’s microscopic morphology,but because of the Pd loading,the Pd@Ti O₂ obtained excellent performance,where the photocurrent density,ABPE,IPCE maximum,and hydrogen production efficiency were 2.36,1.82,2.30,and 4.65 times higher than those of the unloaded Pd sample,respectively.These tests indicated that the photoelectric performance of the Pd-loaded Ti O₂ nanorods was much higher than that of the unloaded Ti O₂ nanorods.（3）Ordered arrays ofα-Fe₂O₃ nanorods were prepared by a simple one-step hydrothermal method for full-spectrum solar water decomposition,and modification methods such as the construction of heterojunctions,Ce³⁺ion doping,and micro-and nanostructure modulation were used to improve the efficiency of the materials for photocatalytic decomposition of water.After testing and characterization,it was found that there was a uniform layer of iron oxide nanorod-like array structure on the surface of the titanium substrate,and mesoporous structures of 5-30 nm existed on the nanorods;the titanium flakes oxidized to Ti O₂ during the annealing process and formed a heterojunction with Fe₂O₃;cerium was successfully doped into the lattice of iron oxide and built up a built-in electric field;under the combined effect of heterojunction and cerium doping,the cerium-doped Ce doping optimized the energy band structure of Fe₂O₃ and improved the PEC performance of Fe₂O₃.PEC performance,resulting in a hydrogen production of 126μmol/cm² for Fe₂O₃.