Preparation Of Metal Foam Supported Titanium-containing Photocatalytic Material And Study On Its Photocatalytic Performance

Excessive consumption of fossil fuels（petroleum,coal,etc.）has caused serious environmental and energy problems.Using solar energy to convert CO₂ into chemicals or fuels is considered one of the most ideal solutions.La₂Ti₂O₇ can be used as a substitute for traditional Ti O₂ catalyst due to its special layered structure and other excellent characteristics.However,the high recombination rate of photogenerated carriers and the easy agglomeration of the powder limit its application.Metal foam is used as the carrier of powder catalyst due to its excellent properties such as high electrical and thermal conductivity.So,in this article,La₂Ti₂O₇ was loaded on nickel foam to improve its photocatalytic performance.In addition,external fields were introduced into the photocatalytic system to further enhance the photocatalytic CO₂conversion effect of semiconductor materials.Therefore,the following researches are carried out in this paper:1.In this paper,nickel foam（NF）was selected as the catalyst carrier,La₂Ti₂O₇/NF composite was synthesized by one-step hydrothermal method,and its photocatalytic CO₂reduction performance was studied.UV-Vis spectrum shows that La₂Ti₂O₇/NF composite photocatalyst has better light absorption ability.It was concluded by experiments that the optimal hydrothermal synthesis conditions of La₂Ti₂O₇/NF catalyst were 200℃,24 h,1 M Na OH.The products of photocatalytic CO₂ and H₂O over pure La₂Ti₂O₇ powder are CO and CH₄,the yields are 7.89μmol·g^-1 and 3.45μmol·g^-1,respectively.The output of La₂Ti₂O₇/NF composite material reached 20.03μmol·g^-1（CO）and 7.17μmol·g^-1（CH₄）after 2.5 hours,which were 2.5 times and 2 times that of pure La₂Ti₂O₇ powder,respectively.The improvement of the photocatalytic performance is because the nickel foam carrier not only well dispersed La₂Ti₂O₇,but its high conductivity is conducive to the transfer of photogenerated electrons.Besides,after introducing an alternating magnetic field（AMF）into the photocatalytic system,the total output of the La₂Ti₂O₇/NF composite catalyst product was further increased(the yield of CO and CH₄were 15.79μmol·g^-1,and CH₄ was 99.18μmol·g^-1,respectively),indicating that the addition of an alternating magnetic field can improve the photocatalytic performance.2.Cu₂O is a narrow band gap semiconductor with a wider range of light absorption.Using it as a catalyst helps to study the effect of alternating magnetic fields on the photocatalytic system.In this paper,x wt%Cu/Cu₂O/Ni（OH）₂/NF（x is in the range of 0.005～0.1 wt%）monolithic catalyst was synthesized by hydrothermal method and chemical reduction method,and the effect of alternating magnetic field on photocatalytic CO₂ reduction was studied.The products of the monolithic catalyst were CO and CH₄,and the optimal loading of Cu/Cu₂O is0.01 wt%.After introducing AMF,the CH₄ yield of 0.01 wt%Cu/Cu₂O/Ni（OH）₂/NF reached167μmol·g^-1,which was 11 and 6 times higher than that of photocatalysis(14.58μmol·g^-1)and magnetic-thermal coupling catalysis(26.75μmol·g^-1),respectively.And the selectivity of CH₄was 96.1%,which was also higher than that of photocatalysis（51.4%）and magnetic-thermal coupling catalysis（50.9%）.According to the temperature measurement,the surface temperature of the catalyst reached 230℃after introducing AMF to the reaction system.This was attributed to the fact that the magnetic nickel foam generates heat through induction heating.The photoelectrochemical measurement showed that AMF can effectively reduce the recombination of photogenerated electrons and holes(compared with the non-light and non-magnetic conditions,under the bias voltage of-1.5 V vs SCE,the current density of light and magnetic is increased by 1.26 m A·cm^-2,which was higher than the current density increment 0.51m A·cm^-2 under light and non-magnetic conditions).Based on the above analysis,it is concluded that introducing AMF to the photocatalytic system can effectively improve the performance of the Cu/Cu₂O/Ni（OH）₂/NF monolithic catalyst for the catalytic conversion of CO₂ and the product selectivity.