Photocatalysis may provide an intriguing approach to nitrogen fixation, which relies on the transfer of photoexcited electrons to the ultrastable N≡N bond. Upon N chemisorption at active sites (e.g., surface defects), the N molecules have yet to receive energetic electrons toward efficient activation and dissociation, often forming a bottleneck. Herein, we report that the bottleneck can be well tackled by refining the defect states in photocatalysts via doping. As a proof of concept, WO ultrathin nanowires are employed as a model material for subtle Mo doping, in which the coordinatively unsaturated (CUS) metal atoms with oxygen defects serve as the sites for N chemisorption and electron transfer. The doped low-valence Mo species play multiple roles in facilitating N activation and dissociation by refining the defect states of WO: (1) polarizing the chemisorbed N molecules and facilitating the electron transfer from CUS sites to N adsorbates, which enables the N≡N bond to be more feasible for dissociation through proton coupling; (2) elevating defect-band center toward the Fermi level, which preserves the energy of photoexcited electrons for N reduction. As a result, the 1 mol % Mo-doped WO sample achieves an ammonia production rate of 195.5 μmol g h, 7-fold higher than that of pristine WO. In pure water, the catalyst demonstrates an apparent quantum efficiency of 0.33% at 400 nm and a solar-to-ammonia efficiency of 0.028% under simulated AM 1.5 G light irradiation. This work provides fresh insights into the design of photocatalyst lattice for N fixation and reaffirms the versatility of subtle electronic structure modulation in tuning catalytic activity.

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Photocatalytic conversion of CO to CH, a carbon-neutral fuel, represents an appealing approach to remedy the current energy and environmental crisis; however, it suffers from the large production of CO and H by side reactions. The design of catalytic sites for CO adsorption and activation holds the key to address this grand challenge. In this Article, we develop highly selective sites for photocatalytic conversion of CO to CH by isolating Cu atoms in Pd lattice. According to our synchrotron-radiation characterizations and theoretical simulations, the isolation of Cu atoms in Pd lattice can play dual roles in the enhancement of CO-to-CH conversion: (1) providing the paired Cu-Pd sites for the enhanced CO adsorption and the suppressed H evolution; and (2) elevating the d-band center of Cu sites for the improved CO activation. As a result, the PdCu-TiO photocatalyst achieves the high selectivity of 96% for CH production with a rate of 19.6 μmol g h. This work provides fresh insights into the catalytic site design for selective photocatalytic CO conversion, and highlights the importance of catalyst lattice engineering at atomic precision to catalytic performance.

Achieving active and stable oxygen evolution reaction (OER) in acid media based on single-atom catalysts is highly promising for cost-effective and sustainable energy supply in proton electrolyte membrane electrolyzers. Here, we report an atomically dispersed Ru1-N4 site anchored on nitrogen-carbon support (Ru-N-C) as an efficient and durable electrocatalyst for acidic OER. The single-atom Ru-N-C catalyst delivers an exceptionally intrinsic activity, reaching a mass activity as high as 3571 A gmetal−1 and turnover frequency of 3348 O2 h−1 with a low overpotential of 267 mV at a current density of 10 mA cm−2. The catalyst shows no evident deactivation or decomposition after 30-hour operation in acidic environment. Operando synchrotron radiation X-ray absorption spectroscopy and infrared spectroscopy identify the dynamic adsorption of single oxygen atom on Ru site under working potentials, and theoretical calculations demonstrate that the O-Ru1-N4 site is responsible for the high OER activity and stability.

Synchrotron FTIR (S-FTIR) microspectroscopy was used to monitor the silk protein conformation in a range of single natural silk fibers (domestic and wild silkworm and spider dragline silk). With the selection of suitable aperture size, we obtained high-resolution S-FTIR spectra capable of semiquantitative analysis of protein secondary structures. For the first time, we have determined from S-FTIR the β-sheet content in a range of natural single silk fibers, 28 ± 4, 23 ± 2, and 17 ± 4% in Bombyx mori, Antheraea pernyi, and Nephila edulis silks, respectively. The trend of β-sheet content in different silk fibers from the current study accords quite well with published data determined by XRD, Raman, and (13)C NMR. Our results indicate that the S-FTIR microspectroscopy method has considerable potential for the study of single natural silk fibers.

Metal‐free polymer photocatalysts have shown great promise for photocatalytic H2O2 production via two‐electron reduction of molecular O2. The other half‐reaction, which is the two‐electron oxidation of water, still remains elusive toward H2O2 production. However, enabling this water oxidation pathway is critically important to improve the yield and maximize atom utilization efficiency. It is shown that introducing acetylene (CC) or diacetylene (CCCC) moieties into covalent triazine frameworks (CTFs) can remarkably promote photocatalytic H2O2 production. This enhancement is inherent to the incorporated carbon–carbon triple bonds which are essential in modulating the electronic structures of CTFs and suppressing charge recombinations. Furthermore, the acetylene and diacetylene moieties can significantly reduce the energy associated with OH* formation and thus enable a new two‐electron oxidation pathway toward H2O2 production. The study unveils an important reaction pathway toward photocatalytic H2O2 production, reflecting that precise control over the chemical structures of polymer photocatalysts is vital to achieve efficient solar‐to‐chemical energy conversion.

Nitrogen fixation in a simulated natural environment (i.e., near ambient pressure, room temperature, pure water, and incident light) would provide a desirable approach to future nitrogen conversion. As the NN triple bond has a thermodynamically high cleavage energy, nitrogen reduction under such mild conditions typically undergoes associative alternating or distal pathways rather than following a dissociative mechanism. Here, we report that surface plasmon can supply sufficient energy to activate N 2 through a dissociative mechanism in the presence of water and incident light, as evidenced by in situ synchrotron radiationbased infrared spectroscopy and near ambient pressure X-ray photoelectron spectroscopy. Theoretical simulation indicates that the electric field enhanced by surface plasmon, together with plasmonic hot electrons and interfacial hybridization, may play a critical role in NN dissociation. Specifically, AuRu coreantenna nanostructures with broadened light adsorption cross section and active sites achieve an ammonia production rate of 101.4 μmol g −1 h −1 without any sacrificial agent at room temperature and 2 atm pressure. This work highlights the significance of surface plasmon to activation of inert molecules, serving as a promising platform for developing novel catalytic systems.

In this work, IR-driven CO 2 overall splitting is first realized by designing an ultrathin intermediate-band semiconductor. Taking the synthetic ultrathin oxygen-deficient cubic WO 3 layers as an example, theoretical calculations unveil that created oxygen vacancies reaching a critical density results in the formation of an intermediate band, verified by synchrotron-radiation photoemission spectra, photoluminescence spectra, and UV-vis-NIR reflectance spectra. Thanks to the suitable band edge positions and the intermediate bands, the oxygen-deficient WO 3 atomic layers achieve IR-driven CO 2 reduction to CO and O 2 .