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 H2 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.
Light‐driven hydrogen production: A carbon/nitrogen steam reforming approach was developed to prepare few‐layered polymeric carbon nitride nanosheets with controlled surface carbon vacancies for photocatalytic hydrogen production. The unique sheet structures with strengthened surface properties endow the polymeric carbon nitride material with more active sites.
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 H2O2 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.
Energy storage and conversion: Self‐supported carbon nitride (CN) aerogels synthesized by self‐assembly of low‐dimensional CN nanostructures are capable of catalyzing H2 and H2O2 evolution reactions under visible‐light irradiation. A simple strategy is used to construct 3D CN aerogel networks that show great potential for solar‐to‐chemical energy conversion by artificial photosynthesis.
Natural photosynthesis serves as a model for energy and chemical conversions, and motivates the search of artificial systems that mimic nature′s energy‐ and electron‐transfer chains. However, ...bioinspired systems often suffer from the partial or even large loss of the charge separation state, and show moderate activity owing to the fundamentally different features of the multiple compounds. Herein, a selenium and cyanamide‐functionalized heptazine‐based melon (DA‐HM) is designed as a unique bioinspired donor–acceptor (D‐A) light harvester. The combination of the photosystem and electron shuttle in a single species, with both n‐ and p‐type conductivities, and extended spectral absorption, endows DA‐HM with a high efficiency in the transfer and separation of photoexcited charge carriers, resulting in photochemical activity. This work presents a unique conjugated polymeric system that shows great potential for solar‐to‐chemical conversion by artificial photosynthesis.
Melon motifs: Biomimetic donor–acceptor motifs were introduced in melon‐based carbon nitride semiconductors to promote exciton dissociation and charge separation. This work presents a simple version of a biomimetic polymeric system that shows great potential for solar‐to‐chemical energy conversion through artificial photosynthesis, and it provides the structural basis for designing photochemical conversion systems having bioinspired functions.
Metal‐free heterostructure photocatalysts composed of black phosphorus (BP) and polymeric carbon nitride (CN) are successfully synthesized via a one‐step liquid exfoliation method assisted by ...sonication. The combination of BP with CN strengthens the visible‐light harvesting ability, facilitates the charge separation in the photocatalytic process, and renders promoted activity of photoinduced molecular oxygen activation, such as superoxide radicals (·O2−) evolution and H2O2 production. This work highlights that coupling semiconductors with well‐matched band levels provide a flexible route to enhance the performance of photocatalysts for producing reactive oxygen species, and gives ideas for the design of highly active and metal‐free materials toward sustainable solar‐to‐chemical energy conversion and environmental remediation.
The black phosphorus and polymeric carbon nitride heterostructure photocatalysts not only exhibit higher visible light absorption ability and accelerated electron–hole separation rate, but also show higher photocatalytic activities in one‐electron and two‐electron reduction of molecular oxygen than pristine carbon nitride. This work promotes the application of metal‐free photocatalysts in solar energy conversion and environmental remediation.
Electrocatalysis is viewed as one of the most effective ways to mitigate the energy problems and produce fuels or value‐added chemicals in a gentle manner. However, duo to the limited electrochemical ...properties of various systems, there is an intensive search for highly efficient electrocatalysts by more rational control over the topographic structure, chemical structure, and electronic structure. At present, the development of electrocatalysts mainly includes two directions: (1) nanoparticle electrocatalysts, and (2) single atom site electrocatalysts (SACs). Nanoparticle and SACs display their own advantages, and have been widely studied in the field of electrocatalysis. Considering the state‐of‐the‐art progress for nanoparticles or SACs, the selection of effective electrocatalysts has been a topic of great research value. Therefore, this paper summarizes the advantages, commonalities, and problems of nanoparticle and SACs, as well as their developing methods and experiences. In addition, the selection of nanoparticle and SACs in electrocatalytic reactions was discussed from the aspects of their respective influencing factors, active sites and synergistic effect. Finally, the research of nanoparticle and single atom sites electrocatalysts were prospected, providing a general guidance for the selection of efficient electrocatalysts.
Nanoparticles and single‐atom site catalysts have shown great potential in the field of electrocatalysis. This paper summarizes the latest research progress on the respective influencing factors, active sites and synergistic effect of metal nanoparticles and single‐atom site electrocatalysts in electrocatalytic reactions, provides general guidance for the selection of high‐efficiency electrocatalysts.
We optimized the crystallization process of carbon nitride polymer by selecting precursors of different polymerization degrees with a molten salt method. Benefiting from the high crystallinity, ...extended π-conjugated system and strong van der-Waals interactions between interlayers, the modified carbon nitride polymer exhibited accelerated charge transport and enhancement in electron induced molecular oxygen activation reactions under visible light, such as hydroxylation of phenylboronic acid and degradation of organic pollutant RhB.
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•Optimized crystallization process for promoting the molecular oxygen activation.•Extended π-conjugated system and tighter layer-to-layer stacks of the photocatalyst.•Promoted photogenic carrier migration and superior photocatalytic performance of CCN.•High yields of phenylboronic acid to phenol and higher activity in Rh B degradation.
Photocatalytic reactive oxygen species (ROS)-induced reactions provide an appealing method to solve the environmental and energy issues, whereas the current oxidation reaction generally suffered from low efficiency and poor selectivity due to uncontrollable O2 activation process. In view of the existence of competitive electron and energy transfer pathway, we propose that highly efficient superoxide radical anion (·O2−) generation can be achieved by optimizing the order degree of the photocatalyst. Herein, by taking carbon nitride polymer as an example, we optimized the crystallization process of carbon nitride polymer by selecting precursors of different polymerization degrees with a molten salt method. Benefiting from the high crystallinity, extended π-conjugated system and strong van der-Waals interactions between interlayers, the modified carbon nitride polymer exhibited accelerated charge transport and enhancement in electron induced molecular oxygen activation reactions under visible light. Consequently, the CCN-P exhibits about 1.5 times higher conversion rate in hydroxylation of phenylboronic acid and over 6-fold faster degradation rate in Rh B organic pollutants photodegradation with respect to pristine carbon nitride. This study provides an in-depth understanding on the optimization of the O2 activation process and the design of advanced photocatalysts.
Crystalline carbon nitride (CCN)‐based semiconductors have recently attracted widespread attention in solar energy conversion. However, further modifying the photocatalytic ability of CCN always ...results in a trade‐off between high crystallinity and good photocatalytic performance. Herein, a facile defect engineering strategy was demonstrated to modify the CCN photocatalysts. Results confirmed that the obtained D‐CCN maintained the high crystallinity; additionally, the hydrogen production rate of D‐CCN was approximately 8 times higher than that of CCN. Particularly, it could produce H2 even if the incident light wavelength extended to 610 nm. The significantly improved photocatalytic activity could be ascribed to the introduction of defects into the CCN polymer network to form the midgap states, which significantly broadened the visible‐light absorption range and accelerated the charge separation for photoredox catalysis.
Effective defects: A facile defect engineering strategy is developed to create defects into crystalline carbon nitride (CCN). The obtained D‐CCN exhibits an enhanced photocatalytic performance owing not only to the maintaining of high crystallinity, but also to the presence of midgap states induced by introducing defects.
While electrochemical N
reduction presents a sustainable approach to NH
synthesis, addressing the emission- and energy-intensive limitations of the Haber-Bosch process, it grapples with challenges in ...N
activation and competing with pronounced hydrogen evolution reaction. Here we present a tandem air-NO
-NO
-NH
system that combines non-thermal plasma-enabled N
oxidation with Ni(OH)
/Cu-catalyzed electrochemical NO
reduction. It delivers a high NH
yield rate of 3 mmol h
cm
and a corresponding Faradaic efficiency of 92% at -0.25 V versus reversible hydrogen electrode in batch experiments, outperforming previously reported ones. Furthermore, in a flow mode concurrently operating the non-thermal plasma and the NO
electrolyzer, a stable NH
yield rate of approximately 1.25 mmol h
cm
is sustained over 100 h using pure air as the intake. Mechanistic studies indicate that amorphous Ni(OH)
on Cu interacts with hydrated K
in the double layer through noncovalent interactions and accelerates the activation of water, enriching adsorbed hydrogen species that can readily react with N-containing intermediates. In situ spectroscopies and density functional theory (DFT) results reveal that NO
adsorption and their hydrogenation process are optimized over the Ni(OH)
/Cu surface. This work provides new insights into electricity-driven distributed NH
production using natural air at ambient conditions.
The CO
2
reduction reaction driven by sustainable electrical energy to value-added hydrocarbons is highly attractive because it can address both energy and environmental issues. The precise and ...rational development of corresponding electrocatalysts is of great importance to these kinds of reactions. Single-atom catalysts with unique electronic structures and coordination environments have become promising candidates, which may offer enhanced electrocatalytic performance. Herein, we summarize the recent development in the efficient fabrication of single-atom catalysts and their further application in CO
2
reduction. The various strategies for SACs preparation and characterization methods are highlighted to give a comprehensive understanding of the relationship between metal active sites and catalytic ability. The reaction mechanisms of electronic CO
2
reduction over single-atom catalysts are elaborated. Finally, the challenges and perspectives for the implementation of single-atom catalysts in CO
2
reduction are discussed.
The techniques for the production of the environment have received attention because of the increasing air pollution, which results in a negative impact on the living environment of mankind. Over the ...decades, burgeoning interest in polymeric carbon nitride (PCN) based photocatalysts for heterogeneous catalysis of air pollutants has been witnessed, which is improved by harvesting visible light, layered/defective structures, functional groups, suitable/adjustable band positions, and existing Lewis basic sites. PCN‐based photocatalytic air purification can reduce the negative impacts of the emission of air pollutants and convert the undesirable and harmful materials into value‐added or nontoxic, or low‐toxic chemicals. However, based on previous reports, the systematic summary and analysis of PCN‐based photocatalysts in the catalytic elimination of air pollutants have not been reported. The research progress of functional PCN‐based composite materials as photocatalysts for the removal of air pollutants is reviewed here. The working mechanisms of each enhancement modification are elucidated and discussed on structures (nanostructure, molecular structue, and composite) regarding their effects on light‐absorption/utilization, reactant adsorption, intermediate/product desorption, charge kinetics, and reactive oxygen species production. Perspectives related to further challenges and directions as well as design strategies of PCN‐based photocatalysts in the heterogeneous catalysis of air pollutants are also provided.
Polymeric carbon nitride‐based photocatalysts have shown great potential in indoor air quality remediation. The state‐of‐the‐art developments in structure regulation including electronic structure, nanostructure, and heterostructure, and their effect on the abatement of air pollution, revealing the structure‐performance relationship in environmental catalysis are discussed here.
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