Hongli Yang,Huilin Hou,Man Yang,Zhongli Zhu,Hui Fu,Dongdong Zhang,Yong Luo,Weiyou Yang
The selective photoreduction of CO 2 into hydrocarbon fuels, such as CH 4 , is highly desirable for sustainable energy but remains a significant challenge due to slow proton-electron transfer processes and competing intermediates. Herein, a novel NiO/MgAl-LDH (NMA-x, LDH represents layered double hydroxide) step-scheme (S-scheme) heterojunction has been engineered via in-situ anchoring MgAl-LDH nanoplates on metal–organic frameworks (MOFs) derived NiO microrods, which improves the CO 2 adsorption capability and specific surface area of NiO. The steered internal electric field in the p-n heterointerface promotes charge separation and attracts a high electron density center on the catalyst surface to favor CH 4 production. Meanwhile, S-scheme photogenerated charge transfer mechanism is proposed by in-situ X-ray photoelectron spectroscopy (XPS), in-situ diffuse reflectance infrared Fourier transform (DRIFT) spectra and density functional theory (DFT) calculation. In this process, photogenerated electrons are transferred from the conduction band (CB) of MgAl-LDH to the valence band (VB) of NiO, facilitating the CHO* species serve as the critical intermediate for producing CH 4 through desired photocatalytic CO 2 reduction. Using pure water as a proton source, the NMA-2 catalyst achieved a high CH 4 selectivity of 91.2% and a yield of 8.98 μmol∙g −1 ∙h −1 , representing significant potential for practical applications. This catalyst outperformed pristine and revitalized NiO by 4.23 and 2.07 times, respectively.
An depth understanding of the fundamental interactions between surface termination and catalytic activity is crucial to prompt the properties of functional perovskite materials. The elastic energy due to size mismatch and electrostatic attraction of the charged Sr dopant by positively charged oxygen vacancies induced inert A-site surface enrichment rearrangement for perovskites. Lower temperatures could reduce A-site enrichment, but it is difficult to form perovskite crystals. La 0.8 Sr 0.2 CoO 3-δ (LSCO) as a model perovskite oxide was modified with additive urea to reduce the crystallization temperature , and suppress Sr segregation. The LSCO catalysts with 600 °C annealing temperature (LSCO-600) exhibited a 19.4-fold reaction reactivity of toluene oxidation than that with 800 °C annealing temperature (LSCO-800). Combined surface-sensitive and depth-resolved techniques for surface and sub-surface analysis, surface Sr enrichment was effectively suppressed due to decreased oxygen vacancy concentration and smaller electrostatic driving force. DFT calculations and in-situ DRIFTs spectra well revealed that tuning the surface composition/termination affected the intrinsic reactivity. The catalyst surface with lower Sr enrichment could easily adsorb toluene, cleave, and decompose benzene rings , thus contributing to toluene degradation to CO 2 . This work demonstrates a green and efficient way to control surface composition and termination at the atomic scale for higher catalytic activity.
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