Defects Tune the Strong Metal–Support Interactions in Copper Supported on Defected Titanium Dioxide Catalysts for CO₂ Reduction

Abstract

A highly active and stable Cu-based catalyst for CO2 to CO conversion was demonstrated by creating a strong metal–support interaction (SMSI) between Cu active sites and the TiO2-coated dendritic fibrous nano-silica (DFNS/TiO2) support. The DFNS/TiO2–Cu10 catalyst showed excellent catalytic performance with a CO productivity of 5350 mmol g–1 h–1 (i.e., 53,506 mmol gCu –1 h–1), surpassing that of almost all copper-based thermal catalysts, with 99.8% selectivity toward CO. Even after 200 h of reaction, the catalyst remained active. Moderate initial agglomeration and high dispersion of nanoparticles (NPs) due to SMSI made the catalysts stable. Electron energy loss spectroscopy confirmed the strong interactions between copper NPs and the TiO2 surface, supported by in situ diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy. The H2-temperature programmed reduction (TPR) study showed α, β, and γ H2-TPR signals, further confirming the presence of SMSI between Cu and TiO2. In situ Raman and UV–vis diffuse reflectance spectroscopy studies provided insights into the role of oxygen vacancies and Ti3+ centers, which were produced by hydrogen, then consumed by CO2, and then again regenerated by hydrogen. These continuous defect generation–regeneration processes during the progress of the reaction allowed long-term high catalytic activity and stability. The in situ studies and oxygen storage complete capacity indicated the key role of oxygen vacancies during catalysis. The in situ time-resolved Fourier transform infrared study provided an understanding of the formation of various reaction intermediates and their conversion to products with reaction time. Based on these observations, we have proposed a CO2 reduction mechanism, which follows a redox pathway assisted by hydrogen.

Disclosing the Reaction Mechanism of CO2 Hydrogenation to Methanol over CuCeOx/TiO2: A Combined Kinetic, Spectroscopic, and Isotopic Study

“…In addition, our recent work further demonstrated that the r-WGSR would be inhibited over CuCeO x /TiO 2 by the partial coating of the Cu surface with TiO x adlayers generated by a strong metal−support interaction effect (SMSI) between Cu and TiO 2 . 10,51,52 SSITKA-DRIFTS/ MS results are also consistent with this conclusion since a low coverage of CO intermediates is obtained when dividing N CO by the total number of surface Cu sites (i.e., θ CO,Cu = 0.0025, Table 2), therefore, suggesting that the copper nanoparticles are (i) being blocked by the SMSI between Cu and TiO 2 and (ii) being partially occupied by spectator formates.…”

Strong Metal‐support Interactions in Photocatalysis: Fundamentals and Design Methods

“…(c) A proposed mechanism for CO 2 reduction to CO on TiO 2 ‐coated dendritic fibrous nano‐silica supported Cu catalysts. Reprinted with permission from [84] . Copyright American Chemical Society, 2023.…”

“…The catalytic activity remained stable after five testing cycles (Figure 11b). A recent study has reported strong metal‐supported interaction on TiO 2 ‐supported Cu catalyst and its use in CO 2 reduction reaction [84] . TiO 2 support partially encapsulated and induced SMSI overlayer around Cu active sites where Ti 3+ species found them strongly bond with copper atoms, accompanying with defective oxygen vacancies on TiO 2 surface.…”

“…The formate intermediates would break down into CO and leave OH on TiO 2 surface which desorbed as water molecules after reacting with another dissociated H species. Afterwards, the catalyst regenerated oxygen vacancies and Ti 3+ species as a fresh one [84] …”

A strong metal–support interaction strategy for enhanced binder-free electrocatalytic nitrate reduction

“…44 It is worth noting that the aggregation of iron nanostructures and the insufficient exposure of active sites caused by high surface magnetism can be effectively addressed through the SMSI between Fe active sites and support materials. 45,46 In this work, we developed a universal strategy that can load Fe NPs on the surface of a series of carbon-based or metal-based supports (such as graphite felt (GF), carbon cloth (CC), carbon paper (CP), copper foam (CF), nickel foam (NF), and iron foam (IF)) to obtain self-supported Fe/support catalysts. The strong interaction between Fe NPs and GF is conducive to increasing the exposure of iron active sites and stability, which shows high electrocatalytic NO 3 RR performance with a 67.7% NO 3 − conversion rate and a 96.6% N 2 selectivity.…”