CO₂ electroreduction to formic acid/formate would contribute to alleviating the energy and climate crisis. This work reports a Bi-based catalyst derived from the in-situ electroreduction of Bi₂O₂CO₃ modified with iodine and pyrenyl-graphdiyne (PGDY) on the surface for efficient electroreduction of CO₂ in acidic electrolyte, with a high partial current density of 98.71 mA·cm⁻² and high Faradaic efficiency (FE) > 90% over the potential range from −1.2 to −1.5 V vs. reversible hydrogen electrode (RHE), as well as the long-term operational stability over 240 h without degradation in H-type cell. Experimental results and density function theory calculations show that the synergistic effect of surface iodine and PGDY is responsible for this active and extremely stable process of CO₂ electroreduction via lowering the energy barriers for formation of *OCHO intermediate, suppressing the competitive HER by enhancing the concentration of both K⁺ and CO₂ at reaction interface, as well as preventing the dissolution and re-deposition of active Bi atoms on surface during catalytic reaction. This work provides new insight into designing highly active and stable electrocatalysts for CO₂ reduction.

The judicious implantation of active metal cations into the surface of semiconductor nanocrystal (NC) through cation-exchange is one of the facile and viable strategies to enhance the activity of catalysts for photocatalytic CO₂ reduction, by shortening the transfer pathway of photogenerated carriers and increasing the active sites simultaneously. However, cation-exchange is hard to achieve for halide perovskite NCs owing to the stable octahedron of [PbX₆]⁴⁻ with strong interaction between halogen and lead. Herein, we report a facile method to overcome this obstacle by replacing partial Br⁻ with acetate (Ac⁻) to generate CsPbBr₃ NC (coded as CsPbBr_3−xAc_x). A small amount of Ac⁻ instead of Br⁻ does not change the crystal structure of halide perovskite. Owing to the weaker interaction between acetate and lead in comparison with bromide, the corresponding octahedron structure containing acetate in CsPbBr_3−xAc_x can be easily opened to realize efficient cation-exchange with Ni²⁺ ions. The resulting high loading amount of Ni²⁺ as active site endows CsPbBr_3−xAc_x with an improved performance for photocatalytic CO₂ reduction under visible light irradiation, exhibiting a significantly increased CO yield of 44.09 μmol·g⁻¹·h⁻¹, which is over 8 and 3 times higher than those of traditional pristine CsPbBr₃ and nickel doped CsPbBr₃ NC, respectively. This work provides a critical solution for the efficient metal doping of low-cost halide perovskite NCs to enhance their photocatalytic activity, promoting their practical applications in the field of photocatalysis.

Sunlight-driven activation of molecular oxygen (O₂) for organic oxidation reactions offers an appealing strategy to cut down the reliance on fossil fuels in chemical industry, yet it remains a great challenge to simultaneously tailor the charge kinetics and promote reactant chemisorption on semiconductor catalysts for enhanced photocatalytic performance. Herein, we report iron sites immobilized on defective BiOBr nanosheets as an efficient and selective photocatalyst for activation of O₂ to singlet oxygen (¹O₂). These Fe³⁺ species anchored by oxygen vacancies can not only facilitate the separation and migration of photogenerated charge carrier, but also serve as active sites for effective adsorption of O₂. Moreover, low-temperature phosphorescence spectra combined with X-ray photoelectron spectroscopy (XPS) and electronic paramagnetic resonance (EPR) spectra under illumination reveal that the Fe species can boost the quantum yield of excited triplet state and accelerate the energy transfer from excited triplet state to adsorbed O₂ via a chemical loop of Fe³⁺/Fe²⁺, thereby achieving highly efficient and selective generation of ¹O₂. As a result, the versatile iron sites on defective BiOBr nanosheets contributes to near-unity conversion rate and selectivity in both aerobic oxidative coupling of amines to imines and sulfoxidation of organic sulfides. This work highlights the significant role of metal sites anchored on semiconductors in regulating the charge/energy transfer during the heterogeneous photocatalytic process, and provides a new angle for designing high-performance photocatalysts.

Reducing the size of heterogeneous nanocatalysts is generally conducive to improving their atomic utilization and activities in various catalytic reactions. However, this strategy has proven less effective for Cu-based electrocatalysts for the reduction of CO₂ to multicarbon (C₂₊) products, owing to the overly strong binding of intermediates on small-sized (< 15 nm) Cu nanoparticles (NPs). Herein, by incorporating pyrenyl-graphdiyne (Pyr-GDY), we successfully endowed ultrafine (~ 2 nm) Cu NPs with a significantly elevated selectivity for CO₂-to-C₂₊ conversion. The Pyr-GDY can not only help to relax the overly strong binding between adsorbed H^* and CO^* intermediates on Cu NPs by tailoring the d-band center of the catalyst, but also stabilize the ultrafine Cu NPs through the high affinity between alkyne moieties and Cu NPs. The resulting Pyr-GDY-Cu composite catalyst gave a Faradic efficiency (FE) for C₂₊ products up to 74%, significantly higher than those of support-free Cu NPs (C₂₊ FE, ~ 2%), carbon nanotube-supported Cu NPs (CNT-Cu, C₂₊ FE, ~ 18%), graphene oxide-supported Cu NPs (GO-Cu, C₂₊ FE, ~ 8%), and other reported ultrafine Cu NPs. Our results demonstrate the critical influence of graphdiyne on the selectivity of Cu-catalyzed CO₂ electroreduction, and showcase the prospect for ultrafine Cu NPs catalysts to convert CO₂ into value-added C₂₊ products.

Graphdiyne (GDY) is emerging as a promising material for various applications owing to its unique structure and fascinating properties. However, the application of GDY in electronics and optoelectronics are still in its infancy, primarily owing to the huge challenge in the synthesis of large-area and uniform GDY film for scalable applications. Here a modified van der Waals epitaxy strategy is proposed to synthesize wafer-scale GDY film with high uniformity and controllable thickness directly on graphene (Gr) surface, providing an ideal platform to construct large-scale GDY/Gr-based optoelectronic synapse array. Essential synaptic behaviors have been realized, and the linear and symmetric conductance-update characteristics facilitate the implementation of neuromorphic computing for image recognition with high accuracy and strong fault tolerance. Logic functions including "NAND" and "NOR" are integrated into the synapse which can be executed in an optical pathway. Moreover, a visible information sensing-memory- processing system is constructed to execute real-time image acquisition, in situ image memorization and distinction tasks, avoiding the time latency and energy consumption caused by data conversion and transmission in conventional visual systems. These results highlight the potential of GDY in applications of neuromorphic computing and artificial visual systems.

A visible-light-response, efficient and robust photo-catalyst for CO₂ reduction is highly desirable. Herein, we demonstrate that single titanium-oxide species implanted in two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) matrix (2D TiO-CN) can efficiently photo-catalyze the reduction of CO₂ to CO under the irradiation of visible light. The synergistic interaction between single titanium oxide species and g-C₃N₄ in 2D TiO-CN not only enhances the separation of photo-excited charges, but also results in visible light response of single titanium-oxide species, realizing high activity of CO₂ photo-reduction with extremely high CO generation rate of 283.9 μmol·h⁻¹·g⁻¹, 5.7, 6.8 and 292.2 times larger than those of TiO₂/CN hybrid material, CN and commercial TiO₂, respectively. Time-resolved fluorescence and electron spin resonance spectroscopy revealed the catalytic mechanism of the fabricated 2D TiO-CN photocatalysts for CO₂ reduction.

Since its discovery, the direct imaging and determination of the crystal structure of few-layer graphdiyne has proven difficult because it is too delicate under irradiation by an electron beam. In this work, the crystal structure of a six-layered graphdiyne nanosheet was directly observed by low-voltage transmission electron microscopy (TEM) using low current density. The combined use of high-resolution TEM (HRTEM) simulation, electron energy-loss spectroscopy, and electron diffraction revealed that the as-synthesized nanosheet was crystalline graphdiyne with a thickness of 2.19 nm (corresponding to a thickness of six layers) and showed ABC stacking. Thus, this work provides direct evidence for the existence and crystal structure of few-layer graphdiyne, which is a new type of two-dimensional carbon material complementary to graphene.