All-inorganic Pb-free bismuth (Bi) halogen perovskite quantum dots (PQDs) with distinct structural and photoelectric properties provide plenty of room for selective photoreduction of CO 2 . However, the efficient conversion of CO 2 -to-CO with high selectivity on Bi-based PQDs driven by solar light remains unachieved, and the precise reaction path/ mechanism promoted by the surface halogen-associated active sites is still poorly understood. Herein, we screen a series of nontoxic and stable Cs 3 Bi 2 X 9 (X = Cl, Br, I) PQDs for selective photocatalytic reduction of CO 2 -to-CO at the gas−solid interface. Among all the reported pure-phase PQDs, the assynthesized Cs 3 Bi 2 Br 9 PQDs exhibited the highest CO 2 -to-CO conversion efficiency generating 134.76 μmol g −1 of CO yield with 98.7% selectivity under AM 1.5G simulated solar illumination. The surface halogen-associated active sites and reaction intermediates were dynamically monitored and precisely unraveled based on in situ DRIFTS investigation. In combination with the DFT calculation, it was revealed that the surface Br sites allow for optimizing the coordination modes of surfacebound intermediate species and reducing the reaction energy of the rate-limiting step of COOH − intermediate formation from • CO 2 − . This work presents a mechanistic insight into the halogen-involved catalytic reaction mechanism in solar fuel production.

Photocatalytic CO2 conversion into valuable solar fuels is highly appealing, but lack of directional charge-transfer channel and insufficient active sites resulted in limited CO2 reduction efficiency and selectivity for most photocatalytic systems. Herein, we designed and fabricated rare-earth La single-atoms on carbon nitride with La–N charge-transfer bridge as the active center for photocatalytic CO2 reaction. The formation of La single-atoms was certified by spherical aberration-corrected HAADF-STEM, STEM-EELS, EXAFS, and theoretical calculations. The electronic structure of the La–N bridge enables a high CO-yielding rate of 92 μmol·g–1·h–1 and CO selectivity of 80.3%, which is superior to most g-C3N4-based photocatalytic CO2 reductions. The CO production rate remained nearly constant under light irradiation for five cycles of 20 h, indicating its stability. The closely combined experimental and DFT calculations clearly elucidated that the variety of electronic states induced by 4f and 5d orbitals of the La single atom and the p–d orbital hybridization of La–N atoms enabled the formation of charge-transfer channel. The La–N charge bridges are found to function as the key active center for CO2 activation, rapid COOH* formation, and CO desorption. The present work would provide a mechanistic understanding into the utilization of rare-earth single-atoms in photocatalysis for solar energy conversion.

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to the resonant plasmonic effect. It was also observed [24,26,27] and calculated [25] that the plasmonic hot spots in metal nanostructures can generate large numbers of energetic electrons. The design of a plasmonic nanocrystal is crucial to create plasmonic hot spots that generate efficiently energetic electrons. In this study, we will address this problem of hot spots and energetic electrons.Here we investigate theoretically the process of generation of hot electrons in nanocrystals with various shapes, such as nanostars (NSTs), nanorods (NRs), and spherical nanoparticles (NPs). The focus will be on the role of plasmonic hot spots in such NCs. In this study, we show that plasmonic NSTs with multiple hot spots are very efficient for generation of energetic electrons. We also compare NSTs with NRs and NPs and discuss two material systems, gold and silver. Silver NCs exhibit much larger rates of generation since the plasmon enhancement in such silver NCs is much stronger than that in the case of gold. The physical reason for the high rates of generation of hot carriers in the silver NCs are the following: (1) The long mean free path of electrons and (2) the narrow and intensive plasmonic resonances. The effect of generation of hot electrons is an essentially quantum effect and comes from the optical absorption processes near the surfaces of a NC. Such surface absorption is, of course, efficient only in relatively small NCs. We, therefore, examine the quantum efficiencies and the quantum plasmonic parameter for NCs of various sizes and shapes. Using such calculations, we show the quantum nature of the generation of energetic carriers in NCs in general.We also should note that the formalism of the paper focuses on the quantum intraband transitions in the NCs made of gold and silver. Such intraband transitions dominate the optical responses of the plasmonic NCs in the spectral intervals λ > 500 nm (gold) and λ > 400 nm (silver). Simultaneously, these spectral intervals are most interesting for the plasmonic effects since the plasmonic peaks in these spectral regions appear to be narrow and strong. [23] Regarding the role of the interband transitions and generation of hot holes in the d-band, one can look into recent review papers (e.g., ref.[23]).Theoretically, the problem of hot electrons has been addressed using several methods: Density matrix formalism combined with time-dependent DFT, perturbative approach for the injection currents, Fermi's golden rule, nonequilibrium Nanostars (NSTs) are spiky nanocrystals (NCs) with plasmonic hot spots. In this study, it is shown that strong electromagnetic fields localized in the NST tips are able to generate large numbers of energetic (hot) electrons, which can be used for photochemistry. To compute plasmonic NCs with complex shapes, a quantum approach based on the effect of surface generation of hot electrons is developed. This approach is then applied to NSTs, nanorods (NRs) and nanospheres. It is found that the plasmonic NSTs with multiple hot spots have the best charact...

Hydrogen storage in chemical compounds is a promising strategy to enable lightweight, high-density, and safe hydrogen technologies. However, the hydrogen release rate from these chemicals is limited by the intrinsic catalytic activity of metal catalysts, which can be enhanced by light irradiation. Here, nanohybrids including a core of plasmonic TiN and multiple Pt nanocrystal catalytic centers are assembled and show, under resonant conditions at 700 nm, hot electron-driven hydrogen evolution from ammonia borane at an apparent quantum yield of 120%. It is also demonstrated that solar irradiation enhances the activity of TiN–Pt nanohybrids by one order of magnitude through two synergistic mechanisms: hot electrons and collective-heating contributions. Using the microscopic calculation of the photo-induced temperature around a single nanocrystal, it is revealed that the collective plasmonic heating regime dominates the macroscopic temperature distribution in the system. The presented data show that plasmonic hot electrons and photothermal heating can be used in synergy to trigger hydrogen release from ammonia borane on demand, providing a general strategy for greatly enhancing the activity of metal catalysts in the dark.