The single-site catalyst (SSC) characteristic of atomically dispersed active centers will not only maximize the catalytic activity,but also provideapromising platform for establishing the structure-activity relationship.H owever,a rbitrary arrangements of active sites in the existed SSCs make it difficult for mechanism understanding and performance optimization. Now, aw ell-defined ultrathin SSC is fabricated by assembly of metal-porphyrin molecules,w hiche nables the precise identification of the active sites for d-orbital energy engineering.The activity of as-assembled products for electrocatalytic CO 2 reduction is significantly promoted via lifting up the energy level of metal d z 2 orbitals,e xhibiting ar emarkable Faradaic efficiency of 96 %a tt he overpotential of 500 mV. Furthermore,aturnover frequency of 4.21 s À1 is achieved with negligible decayo ver4 8h.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.Figure 5. DFT calculation of electrocatalytic CO 2 reduction on STPyP-Co.A)Calculated free-energys tates of CO 2 reduction to CO on STPyP-Co and MTPyP-Co. B) Optimized geometry of intermediate [STPyP-Co-COOH].C ),D) Spatial representationo fHOMO orbital of [STPyP-Co-COOH] and [MTPyP-Co-COOH] intermediates, respectively.
Photocatalytic conversion of methane to valueadded products under mild conditions, which represents a long sought-after goal for industrial sustainable production, remains extremely challenging to afford high production and selectivity using cheap catalysts. Herein, we present the crystal phase engineering of commercially available anatase TiO 2 via simple thermal annealing to optimize the structure−property correlation. A biphase catalyst with anatase (90%) and rutile (10%) TiO 2 with the optimal phase interface concentration exhibits exceptional performance in the oxidation of methane to formaldehyde under the reaction conditions of water solvent, oxygen atmosphere, and full-spectrum light irradiation. An unprecedented production of 24.27 mmol g cat −1 with an excellent selectivity of 97.4% toward formaldehyde is acquired at room temperature after a 3 h reaction. Both experimental results and theoretical calculations disclose that the crystal phase engineering of TiO 2 lengthens the lifetime of photogenerated carriers and favors the formation of intermediate methanol species, thus maximizing the efficiency and selectivity in the aerobic oxidation of methane to formaldehyde. More importantly, the feasibility of the scale-up production of formaldehyde is demonstrated by inventing a "pause−flow" reactor. This work opens the avenue toward industrial methane transformation in a sustainable and economical way.
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