Rongjie Li

Precisely engineering the coordination shells of single‐atom catalysts (SACs) through defect control represents a powerful yet largely underexplored strategy to tailor their microenvironment and activity. Herein, Ru single atoms (SAs) and cadmium vacancies (V _Cd ) are synergistically introduced into CdS nanoparticles coupled with Ti ₃ C ₂ T _x MXene, forming Ru‐Cd _1‐x S/Ti ₃ C ₂ T _x Schottky junctions with asymmetric Ru‒S ₃ ‒V _Cd motifs at both the surface and interface. Notably, the second‐shell V _Cd cooperates with the Ru SAs to downshift the p‐band center ( ε _p ) and optimize H 1s‐p antibonding orbital occupancy, enabling adjacent S sites to attain a near‐ideal hydrogen adsorption free energy (ΔG _H* = −0.03 eV) and a ΔG _2H* value of 0.23 eV for the dihydrogen intermediate. Concurrently, V _Cd ‐mediated Ru─O covalent bonds act as atomic bridges at the heterointerface, amplifying the built‐in electric field (BIEF) by 2.56 times and accelerating interfacial photoexcited charge transfer in 1.3 ps. With an ultralow Ru loading of 0.1 wt.%, the optimal Ru _0.1 ‐Cd _1‐x S/Ti ₃ C ₂ T _x ‐1.5 wt.% composite achieves a photocatalytic H ₂ evolution rate of 48.58 mmol g ⁻¹ h ⁻¹ , surpassing pristine CdS by a factor of 45.4, along with an apparent quantum efficiency (AQE) of 16.2% at 420 nm. This work establishes a new strategy for atomic‐level microenvironment engineering of SACs across both surfaces and heterointerfaces.

Emerging step‐scheme (S‐scheme) heterostructures hold unique superiority in steering directional charge transport and reinforcing redox capacity, yet rational modification of S‐scheme heterostructures by single atoms (SAs) for efficient photocatalytic H₂ evolution is rarely reported. In this work, Pd SAs‐modulated organic–inorganic g‐C₃N₄/CdS S‐scheme heterostructures are designed and prepared by a one‐pot mechanochemical approach allowing for g‐C₃N₄ nanosheets/CdS nanoparticles to confine atomically dispersed Pd co‐catalysts. The g‐C₃N₄/CdS S‐scheme charge‐transfer pathway is corroborated by a combination of in situ irradiated X‐ray photoelectron spectroscopy, electron paramagnetic resonance, and Kelvin probe force microscopy. Density functional theory (DFT) calculations, high‐angle annular dark‐field scanning transmission electron microscopy, and X‐ray absorption fine structure identify Pd‐S₃ and Pd‐N₂ atomic moieties underpinned by the electronic interaction between Pd SAs and g‐C₃N₄/CdS heterostructures, in which the d‐band center of Pd SAs is optimized for proton adsorption thermodynamically. Further, the g‐C₃N₄/CdS S‐scheme heterostructures alongside Pd SAs in concert boost the rapid migration of photogenerated electrons (1.05 ps) via Pd─S and Pd─N bond‐derived channels. A maximal H₂ evolution rate of 85.66 mmol h⁻¹ g⁻¹ is achieved by 1 wt% Pd‐20 wt% g‐C₃N₄/CdS hierarchical composites. This work may guide the design of high‐efficiency S‐scheme‐based photocatalysts for solar‐to‐H₂ conversion and beyond.

Artificial photosynthesis enables direct solar‐to‐chemical energy conversion aimed at mitigating environmental pollution and producing solar fuels and chemicals in a green and sustainable approach, and efficient, robust, and low‐cost photocatalysts are the heart of artificial photosynthesis systems. As an emerging new class of cocatalytic materials, single‐atom catalysts (SACs) and dual‐atom catalysts (DACs) have received a great deal of current attention due to their maximal atom utilization and unique photocatalytic properties, whereas noble‐metal‐free ones impart abundance, availability, and cost‐effectiveness allowing for scalable implementation. This review outlines the fundamental principles and synthetic methods of SACs and DACs and summarizes the most recent advances in SACs (Co, Fe, Cu, Ni, Bi, Al, Sn, Er, La, Ba, etc.) and DACs (CuNi, FeCo, InCu, KNa, CoCo, CuCu, etc.) based on non‐noble metals, confined on an arsenal of organic or inorganic substrates (polymeric carbon nitride, metal oxides, metal sulfides, metal–organic frameworks, carbon, etc.) acting as versatile scaffolds in solar‐light‐driven photocatalytic reactions, including hydrogen evolution, carbon dioxide reduction, methane conversion, organic synthesis, nitrogen fixation, hydrogen peroxide production, and environmental remediation. The review concludes with the challenges, opportunities, and future prospects of noble‐metal‐free SACs and DACs for artificial photosynthesis.