Rational Regulation of Electronic Structure in Layered Double Hydroxide Via Vanadium Incorporation to Trigger Highly Selective CO2 Photoreduction to CH4.

ABSTRACT

To realize excellent selectivity of CH4 in CO2 photoreduction (CO2 PR) is highly desirable, yet which is challenging due to the limited active sites for CH4 generation and severe electron-hole recombination on photocatalysts. Herein, based on the theoretically calculated effects of vanadium incorporation into the laminate of layered double hydroxides (LDHs), V into NiAl-LDH to synthesize a series of LDHs with various V contents is introduced. NiV-LDH is revealed to afford a high CH4 selectivity (78.9%), and extremely low H2 selectivity (only 0.4%) under λ > 400 nm irradiation. By further tuning the molar ratio of Ni to V, a CH4 selectivity of as high as 90.1% is achieved on Ni4 V-LDH, and H2 is completely prohibited on Ni2 V-LDH. Fine structural characterizations and comprehensive optical and electrochemical studies uncover V incorporation creates the lower-valence Ni species as active sites for generating CH4 , and enhances the generation, separation, and transfer of photogenerated carriers.