Tri-s-triazine-based crystalline carbon nitride nanosheets (CCNNSs) have been successfully extracted via a conventional and cost-effective sonication-centrifugation process. These CCNNSs possess a highly defined and unambiguous structure with minimal thickness, large aspect ratios, homogeneous tri-s-triazine-based units, and high crystallinity. These tri-s-triazine-based CCNNSs show significantly enhanced photocatalytic hydrogen generation activity under visible light than g-C N , poly (triazine imide)/Li Cl , and bulk tri-s-triazine-based crystalline carbon nitrides. A highly apparent quantum efficiency of 8.57% at 420 nm for hydrogen production from aqueous methanol feedstock can be achieved from tri-s-triazine-based CCNNSs, exceeding most of the reported carbon nitride nanosheets. Benefiting from the inherent structure of 2D crystals, the ultrathin tri-s-triazine-based CCNNSs provide a broad range of application prospects in the fields of bioimaging, and energy storage and conversion.

Ternary boron carbon nitride (BCN) semiconductors have been developed as emerging metal-free photocatalysts for visiblelight reduction of CO 2 , but the achieved efficiency is still not satisfying. Herein, we report that the CO 2 photoreduction performance of a bulk BCN semiconductor can be substantially improved by surface engineering with CdS nanoparticles. The CdS/BCN photocatalysts are characterized completely by diverse tests (e.g., XRD, FTIR, XPS, DRS, SEM, TEM, N 2 sorption, PL, and transient photocurrent spectroscopy). Performance of the CdS/BCN heterostructures is evaluated by reductive CO 2 conversion reactions with visible light under benign reaction conditions. Compared with bare BCN material, the optimized CdS/BCN photocatalyst exhibits a 10-fold-enhanced CO 2 reduction activity and high stability, delivering a considerable CO production rate of 12.5 μmol h −1 (250 μmol h −1 g −1 ) with triethanolamine (TEOA) as the reducing agent. The reinforced photocatalytic CO 2 reduction activity is mainly assigned to the obviously improved visible-light harvesting and the greatly accelerated separation/transport kinetics of light-triggered electron−hole pairs. Furthermore, a possible visible-light-induced CO 2 reduction mechanism is proposed on the basis of photocatalytic and photo(electro)chemical results.

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The delamination of layered crystals that produces single or few-layered nanosheets while enabling exotic physical and chemical properties, particularly for semiconductor functions in optoelectronic applications, remains a challenge. Here, we report a facile and green approach to prepare few-layered polymeric carbon nitride (PCN) semiconductors by a one-step carbon/nitrogen steam reforming reaction. Bulky PCN, obtained from typical precursors including urea, melamine, dicyandiamide, and thiourea, are exfoliated into few-layered nanosheets, while engineering its surface carbon vacancies. The unique sheet structures with strengthened surface properties endow PCNs with more active sites, and an increased charge separation efficiency with a prolonged charge lifetime, drastically promoting their photoredox performance. After an assay of a H evolution reaction, an apparent quantum yield of 11.3 % at 405 nm was recorded for the PCN nanosheets, which is much higher than those of PCN nanosheets. This delamination method is expandable to other carbon-based 2D materials for advanced applications.

Aerogel structures have attracted increasing research interest in energy storage and conversion owing to their unique structural features, and a variety of materials have been engineered into aerogels, including carbon-based materials, metal oxides, linear polymers and even metal chalcogenides. However, manufacture of aerogels from nitride-based materials, particularly the emerging light-weight carbon nitride (CN) semiconductors is rarely reported. Here, we develop a facile method based on self-assembly to produce self-supported CN aerogels, without using any cross-linking agents. The combination of large surface area, incorporated functional groups and three-dimensional (3D) network structure, endows the resulting freestanding aerogels with high photocatalytic activity for hydrogen evolution and H O production under visible light irradiation. This work presents a simple colloid chemistry strategy to construct 3D CN aerogel networks that shows great potential for solar-to-chemical energy conversion by artificial photosynthesis.

Developing electrocatalysts with high compatibility to the reaction systems with complicated chemical properties represents an important frontier of catalyst design. Herein, a strategy by engineering a multifunctional collaborative catalytic interface to propel the hydrogen evolution reaction (HER) in the full pH range and seawater is reported. Collaborative catalytic interfaces among MXene, bimetallic carbide, and hybridized carbon are demonstrated to afford overall enhancement in electrical conductivity, exposure of reactive sites, water dissociation kinetics, H+/water adsorption, and intermediate H binding capability, which satisfy highly variable chemical environment for HER under different pH conditions. Therefore, the HER performance of resultant electrocatalysts can compete with commercial Pt/C in 0.5 m H2SO4 or 1.0 m KOH but outperform it under pH 2.2–11.2. They also show exceptional performance for HER in natural seawater with stringent requirements in catalytic activity and stability, exhibiting the best combination of Pt‐like activity, long durability (225 h, 64 times that of Pt/C), and 98% Faradaic efficiency, comparable with commercial Pt/C and the best documented electrocatalysts by far. This work may shed fresh light into the design of effective electrocatalytic interface for regulating the energy chemistry over wide operation conditions, and also inspires the exploration of hydrogen energy utilization technologies and beyond.

Photosynthetic conversion of CO2 into fuel and chemicals is a promising but challenging technology. The bottleneck of this reaction lies in the activation of CO2, owing to the chemical inertness of linear CO2. Herein, we present a defect‐engineering methodology to construct CO2 activation sites by implanting carbon vacancies (CVs) in the melon polymer (MP) matrix. Positron annihilation spectroscopy confirmed the location and density of the CVs in the MP skeleton. In situ diffuse reflectance infrared Fourier transform spectroscopy and a DFT study revealed that the CVs can function as active sites for CO2 activation while stabilizing COOH* intermediates, thereby boosting the reaction kinetics. As a result, the modified MP‐TAP‐CVs displayed a 45‐fold improvement in CO2‐to‐CO activity over the pristine MP. The apparent quantum efficiency of the MP‐TAP‐CVs was 4.8 % at 420 nm. This study sheds new light on the design of high‐efficiency polymer semiconductors for CO2 conversion.

Multilevel hollow structures provide a superior material platform to conventional designs for exceptional functionalities enabled by wide tailorability of interfacial properties and local microenvironments. Herein, a facile strategy is reported for tailoring the electrocatalytic performance of a low-Pt catalyst over a wide range of pH conditions using multilevel hollow MXene with sufficient diffusion channels, multiple reactive surface areas, and robust frameworks with high conductivity and hydrophilic and aggregation resistance. Their synergy with ultrafine Pt creates efficient multifunctional catalytic interfaces with high Pt utilization, and overall enhanced charge transport, H + /water adsorption activation, intermediate H binding, and ionic/mass exchange. The resultant catalyst fully exceeds the commercial 20% Pt/C by 10-20 folds in mass activity for hydrogen evolution through the full pH range. The highest mass activity of 12.94 A mg Pt −1 is achieved in an alkaline electrolyte with 1/8 Pt usage of 20% Pt/C. This catalyst also exhibits the best combination of high activity, long lifetime (250 h, 31 times of Pt/C), and nearly 100% Faradaic efficiency among 20% Pt/C (8 h) and documented electrocatalysts (10-100 h) for hydrogen production in natural seawater. This study offers an effective interface-engineering strategy to regulate electrocatalysis over broad chemical conditions to meet the complicated application criteria.