Synergy of Pd atoms and oxygen vacancies on In2O3 for methane conversion under visible light

Abstract

Methane (CH4) oxidation to high value chemicals under mild conditions through photocatalysis is a sustainable and appealing pathway, nevertheless confronting the critical issues regarding both conversion and selectivity. Herein, under visible irradiation (420 nm), the synergy of palladium (Pd) atom cocatalyst and oxygen vacancies (OVs) on In2O3 nanorods enables superior photocatalytic CH4 activation by O2. The optimized catalyst reaches ca. 100 μmol h−1 of C1 oxygenates, with a selectivity of primary products (CH3OH and CH3OOH) up to 82.5%. Mechanism investigation elucidates that such superior photocatalysis is induced by the dedicated function of Pd single atoms and oxygen vacancies on boosting hole and electron transfer, respectively. O2 is proven to be the only oxygen source for CH3OH production, while H2O acts as the promoter for efficient CH4 activation through ·OH production and facilitates product desorption as indicated by DFT modeling. This work thus provides new understandings on simultaneous regulation of both activity and selectivity by the synergy of single atom cocatalysts and oxygen vacancies.

Sulfur-Induced Vacancies in Ba2Bi1.4Nb0.6O6 Promoting Photocatalytic Tetracycline Hydrochloride Degradation

“…Raman spectra (Figure S4) indicate enhanced structural asymmetry caused by the O/S vacancies. It is believed that O/S vacancies are the active sites for light absorption, favoring the photocatalysis …”

“…Introducing heteroatoms, such as N and S, is a widely used strategy to reduce the band gap and enhance the light absorption capacity. For instance, (Ga 1– x Zn x ) (N 1– x O x ), LaMg 1/3 Ta 2/3 O 2 N, BaTaO 2 N, SrNbO 2 N, LaTiO 2 N, Sm 2 Ti 2 S 2 O 5 , and Y 2 Ti 2 O 5 S 2 were reported with a reduced band gap compared to that of their pristine oxide counterparts. − Recently, another effective approach to boost the photocatalytic activity is engineering of oxygen vacancies (O v ). − Semiconductors with vacancies can form new states in the band gap and thus narrow the band gap, and these vacancies act as electron capture centers, improving photocatalytic activities. ,, However, oxygen vacancies may also serve as charge recombination centers . Researchers therefore have made many efforts to control the oxygen vacancies.…”

Photocatalytic CO2reduction on Cu single atoms incorporated in ordered macroporous TiO2toward tunable products

“…8b), the coexistence of *CO and *CHO intermediates is a crucial clue to speculate that the formation of C 2 H 4 follows the pathway of the *COCHO intermediate from dimerization between *CO and *CHO. Therefore, the possible reaction pathways of photocatalytic CO 2 reduction in the present gas-solid and liquid-solid systems are described in eqn (1)-( 5) and ( 6)- (11), respectively, where * denotes the catalytically active sites on the photocatalyst and ↑ represents the release of the gas product.…”

“…Therefore, various metal cocatalysts including noble metals, transition metals and rare Earth metals, have been prepared in SA sites to increase the photocatalytic efficiency. [8][9][10][11][12] Among them, copper (Cu) has been identified as one of the most promising cocatalysts to convert CO 2 into various hydrocarbons owing to its optimum binding ability with CO 2 and reaction intermediates. [13][14][15][16] The individual Cu atoms immobilized on light-harvesting semiconductors can act as excellent active sites for activating CO 2 molecules and stabilizing reaction intermediates in the photocatalytic CO 2 reduction reaction.…”

Insights on Carbon Neutrality by Photocatalytic Conversion of Small Molecules into Value-Added Chemicals or Fuels

“…Besides, the in situ XAFS is also a promising way to monitor the change of catalytic active sites under real reaction conditions . Very recently, the extend X-ray absorption fine structure (EXAFS) was employed in our group to prove the existence of a single Pd atom on Pd-loaded defective In 2 O 3 with oxygen vacancies . Additionally, we also used the EXAFS technique to confirm the existence of the iron in the form of small clusters or even a single atom on the Fe-loaded TiO 2 photocatalyst …”