Semiconductor‐based photocatalysis as a productive technology furnishes a prospective solution to environmental and renewable energy issues, but its efficiency greatly relies on the effective bulk ...and surface separation of photoexcited charge carriers. Exploitation of atomic‐level strategies allows in‐depth understanding on the related mechanisms and enables bottom‐up precise design of photocatalysts, significantly enhancing photocatalytic activity. Herein, the advances on atomic‐level charge separation strategies toward developing robust photocatalysts are highlighted, elucidating the fundamentals of charge separation and transfer processes and advanced probing techniques. The atomic‐level bulk charge separation strategies, embodied by regulation of charge movement pathway and migration dynamic, boil down to shortening the charge diffusion distance to the atomic‐scale, establishing atomic‐level charge transfer channels, and enhancing the charge separation driving force. Meanwhile, regulating the in‐plane surface structure and spatial surface structure are summarized as atomic‐level surface charge separation strategies. Moreover, collaborative strategies for simultaneous manipulation of bulk and surface photocharges are also introduced. Finally, the existing challenges and future prospects for fabrication of state‐of‐the‐art photocatalysts are discussed on the basis of a thorough comprehension of atomic‐level charge separation strategies.
Semiconductor photocatalytic efficiency greatly relies on effective charge separation. The recent progress of atomic‐level strategies for promoting charge separation and migration in the bulk, on the surface, and both bulk and surface of a photocatalyst are highlighted and a guideline for the bottom‐up design of high‐performance photocatalysts suggested.
Photothermal CO
2
reduction is an efficient and sustainable catalytic path for CO
2
treatment. Here, we successfully fabricated a novel series of Ni-based catalysts (Ni-
x
) via H
2
reduction of ...NiAl-layered double hydroxide nanosheets at temperatures (
x
) ranging from 300 to 600 °C. With the increase of the reduction temperature, the methane generation rate of the Ni-
x
catalyst for photothermal CO
2
hydrogenation gradually increased under ultraviolet-visible-infrared (UV-vis-IR) irradiation in a flow-type system. The Ni-600 catalyst showed a CO
2
conversion of 78.4%, offering a CH
4
production rate of 278.8 mmol·g
−1
h
−1
, with near 100% selectivity and 100 h long-term stability. Detailed characterization analyses showed metallic Ni nanoparticles supported on amorphous alumina are the catalytically active phase for CO
2
methanation. This study provides a possibility for large-scale conversion and utilization of CO
2
from a sustainable perspective.
With the ambition of solving the challenges of the shortage of fossil fuels and their associated environmental pollution, visible‐light‐driven splitting of water into hydrogen and oxygen using ...semiconductor photocatalysts has emerged as a promising technology to provide environmentally friendly energy vectors. Among the current library of developed photocatalysts, organic conjugated polymers present unique advantages of sufficient light‐absorption efficiency, excellent stability, tunable electronic properties, and economic applicability. As a class of rising photocatalysts, organic conjugated polymers offer high flexibility in tuning the framework of the backbone and porosity to fulfill the requirements for photocatalytic applications. In the past decade, significant progress has been made in visible‐light‐driven water splitting employing organic conjugated polymers. The recent development of the structural design principles of organic conjugated polymers (including linear, crosslinked, and supramolecular self‐assembled polymers) toward efficient photocatalytic hydrogen evolution, oxygen evolution, and overall water splitting is described, thus providing a comprehensive reference for the field. Finally, current challenges and perspectives are also discussed.
Molecular design strategies of various conjugated polymers for photocatalytic water splitting are reviewed. The structure–property relationships between functional groups, building blocks, and photocatalytic water splitting in a variety of conjugated polymers are explored. Furthermore, key factors that contribute to a highly efficient polymer photocatalyst in visible‐light‐driven water splitting are outlined.
Abstract
The electrochemical CO
2
reduction reaction (CO
2
RR) represents a very promising future strategy for synthesizing carbon-containing chemicals in a more sustainable way. In spite of great ...progress in electrocatalyst design over the last decade, the critical role of wettability-controlled interfacial structures for CO
2
RR remains largely unexplored. Here, we systematically modify the structure of gas-liquid-solid interfaces over a typical Au/C gas diffusion electrode through wettability modification to reveal its contribution to interfacial CO
2
transportation and electroreduction. Based on confocal laser scanning microscopy measurements, the Cassie-Wenzel coexistence state is demonstrated to be the ideal three phase structure for continuous CO
2
supply from gas phase to Au active sites at high current densities. The pivotal role of interfacial structure for the stabilization of the interfacial CO
2
concentration during CO
2
RR is quantitatively analysed through a newly-developed in-situ fluorescence electrochemical spectroscopic method, pinpointing the necessary CO
2
mass transfer conditions for CO
2
RR operation at high current densities.
Prompt recombination of photogenerated electrons and holes in bulk and on the surface of photocatalysts harshly impedes the photocatalytic efficiency. However, the simultaneous manipulation of ...photocharges in the two locations is challenging. Herein, the synchronous promotion of bulk and surface separation of photoinduced charges for prominent CO2 photoreduction by coupling macroscopic spontaneous polarization and surface oxygen vacancies (OVs) of BiOIO3 single crystals is reported. The oriented growth of BiOIO3 single‐crystal nanostrips along the 001 direction, ensuing substantial well‐aligned IO3 polar units, renders a large enhancement for the macroscopic polarization electric field, which is capable of driving the rapid separation and migration of charges from bulk to surface. Meanwhile the introduction of surface OVs establishes a local electric field for charge migration to catalytic sites on the surface of BiOIO3 nanostrips. Highly polarized BiOIO3 nanostrips with ample OVs demonstrate outstanding CO2 reduction activity for CO production with a rate of 17.33 µmol g−1 h−1 (approximately ten times enhancement) without any sacrificial agents or cocatalysts, being one of the best CO2 reduction photocatalysts in the gas–solid system reported so far. This work provides an integrated solution to governing charge movement behavior on the basis of collaborative polarization from bulk and surface.
Collaborative polarization by macroscopic spontaneous polarization and surface oxygen vacancies induces efficient bulk and surface charge separation of BiOIO3 nanostrips, which gives rise to extraordinary CO2 photoreduction activity with a CO evolution rate of 17.33 µmol g−1 h−1, over ten times that of BiOIO3 nanoparticles, also outperforming most previously reported high‐performance photocatalysts.
Thin layer fabrication and crystal facet engineering favor the prompt charge transfer from bulk to the surface of a material and spatial charge separation among different facets, tremendously ...benefitting photocatalytic activity. However, the thickness and surface facet composition are considered as two entwined characteristics of layered materials with well‐defined and tunable shapes, which possess great promise to achieve the simultaneous manipulation of charge transfer and spatial separation. Herein, it is demonstrated that one solution for the aforementioned issue by controllably regulating the surface {010}/{100} facet junctions of a layered thickness‐tunable bismuth‐based material, BiOIO3. The attenuation in thickness of BiOIO3 nanoplates shortens the diffusion pathway of charge carriers, and more importantly the tuning of nanolayer thickness renders the ratio variation of the top {010} facet to the lateral {100} facet, which dominates the spatial separation of photogenerated electrons and holes. As a result, the highest CO evolution rate from CO2 reduction over BiOIO3 nanoplates with the optimal thickness and ratio of exposed facets reaches 5.42 µmol g−1 h−1, over 300% that of the bulk counterpart (1.77 µmol g−1 h−1). This work paves a new way for governing charge movement behaviors on the basis of the synergistic engineering of layer structure and exposing facets.
The interlayer charge migration and surface spatial charge separation are synchronously optimized through controllable regulation of the {010}/{100} facet junctions of a layered bismuth‐based material—BiOIO3, which results in efficient photocatalytic CO2 reduction for CO evolution.
Herein, this work constructs a three-dimensional porous graphitic carbon nitride assembled by highly crystalline and ultrathin nanosheets (3D g-C3N4 NS). 3D g-C3N4 NS could directly split pure water ...into H2 and O2 with high evolution rate up to 101.4 and 49.1 μmol g−1 h−1 under visible light, respectively, approximately 11.8 and 5.1 times higher than bulk g-C3N4 and g-C3N4 NS. Besides, it achieves a notable apparent quantum yield of 1.4% at 420 nm, significantly superior to previously reported Pt/g-C3N4. The efficient activity of 3D g-C3N4 NS is mainly attributed to its 3D interconnected open-framework, assembled by highly crystalline ultrathin nanosheet unit, provides a pathway for faster charge carrier transport. Moreover, benefitting from its 3D structure for preventing agglomeration of nanosheets, 3D g-C3N4 NS is stable for more than 100 h of overall water splitting reaction.
Three-dimensional porous g-C3N4 assembled by highly crystalline and ultrathin nanosheets is successfully constructed, and could efficiently split pure water into H2 and O2 with a notable quantum yield as high as 1.4% at 420 nm. Besides, it still remains stable for more than 100 h of overall water splitting reaction. Display omitted
•Three-dimensional porous g-C3N4 nanosheets (3D U-C3N4 NS) assembled by ultrathin nanosheets was successfully fabricated.•3D U-C3N4 NS could directly split pure water into H2 and O2 with quite high evolution rate under visible light.•3D U-C3N4 NS achieved a notable quantum yield of 1.4% at 420 nm, significantly superior to previously reported Pt/g-C3N4.•3D U-C3N4 NS could still remain stable for more than 100 h of overall water splitting reaction.
Piezoelectric‐based catalysis that relies on the charge energy or separation efficiency of charge carriers has attracted significant attention. The piezo‐potential induced by strain or stress can ...induce a giant electric field, which has been demonstrated to be an effective means for charge energy shifting or transferring electrons and holes. In recent years, intense efforts have been made in this subject, and the research has mainly focussed on two aspects: i) Alteration of surface charge energy by piezo‐potential in piezocatalysis; ii) the separation of photo‐generated charge carriers and the catalytic activity enhancement of an integrated piezoelectric semiconductor or coupled system composed of piezoelectrics and semiconductors. Systematically summarizing the advances of the above two aspects is helpful in the context of deepening understanding of the relevant issues and developing new ideas for piezoelectric‐based catalysis. In this review, a comprehensive summary on piezocatalysis and piezo‐photocatalysis is provided. The charge transfer behaviors and catalytic mechanisms over a large variety of piezocatalysts and piezo‐photocatalysts are systematically analyzed. In addition, the types of mechanical energy, strategies for enhancing piezocatalysis, and the advanced applications of piezocatalysis and piezo‐photocatalysis are discussed. Finally, the promising development directions of piezocatalysis and piezo‐photocatalysis, such as materials, assembly forms, and applications in the future are proposed.
Mechanical energy and solar energy can enable charge energy alteration or effective separation of electron–hole pairs, which trigger various catalytic reactions. The recent research progress on piezocatalysis and piezo‐photocatalysis is summarized, concentrating especially on the typical piezocatalysts, mechanical energy forms, piezocatalysis modulation strategies, piezo‐photocatalyst types, and catalytic applications to offer a guideline for the development of piezoelectric‐based catalysts.
There is interest in metal single atom catalysts due to their remarkable activity and stability. However, the synthesis of metal single atom catalysts remains somewhat ad hoc, with no universal ...strategy yet reported that allows their generic synthesis. Herein, we report a universal synthetic strategy that allows the synthesis of transition metal single atom catalysts containing Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Pt or combinations thereof. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and extended X-ray absorption fine structure spectroscopy confirm that the transition metal atoms are uniformly dispersed over a carbon black support. The introduced synthetic method allows the production of carbon-supported metal single atom catalysts in large quantities (>1 kg scale) with high metal loadings. A Ni single atom catalyst exhibits outstanding activity for electrochemical reduction of carbon dioxide to carbon monoxide, achieving a 98.9% Faradaic efficiency at -1.2 V.
Fe single‐atom catalysts (Fe SACs) with atomic FeNx active sites are very promising alternatives to platinum‐based catalysts for the oxygen reduction reaction (ORR). The pyrolysis of metal–organic ...frameworks (MOFs) is a common approach for preparing Fe SACs, though most MOF‐derived catalysts reported to date are microporous and thus suffer from poor mass transfer and a high proportion of catalytically inaccessible FeNx active sites. Herein, NH2‐MIL‐101(Al), a MOF possessing a mesoporous cage architecture, is used as the precursor to prepare a series of N‐doped carbon supports (denoted herein as NC‐MIL101‐T) with a well‐defined mesoporous structure at different pyrolysis temperatures. The NC‐MIL101‐T supports are then impregnated with a Fe(II)‐phenanthroline complex, and heated again to yield Fe SAC‐MIL101‐T catalysts rich in accessible FeNx single atom sites. The best performing Fe SAC‐MIL101‐1000 catalyst offers outstanding ORR activity in alkaline media, evidenced by an ORR half‐wave potential of 0.94 V (vs RHE) in 0.1 m KOH, as well as excellent performance in both aqueous primary zinc–air batteries (a near maximum theoretical energy density of 984.2 Wh kgZn−1) and solid‐state zinc–air batteries (a peak power density of 50.6 mW cm−2 and a specific capacity of 724.0 mAh kgZn−1).
Mesoporous Fe single‐atom catalysts (Fe SAC‐MIL101‐T) are successfully synthesized using NH2‐MIL‐101(Al)‐derived N‐doped carbon as supports. The abundant mesopores in the supports promote mass transport during the oxygen reduction reaction (ORR) and ensure a high proportion of FeNx sites are accessible. Fe SAC‐MIL101‐1000 demonstrates outstanding activity for ORR and excellent performance in both aqueous and solid‐state zinc–air batteries.
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