Supported metal nanoparticles are the most widely investigated heterogeneous catalysts in catalysis community. The size of metal nanostructures is an important parameter in influencing the activity of constructed catalysts. Especially, as coordination unsaturated metal atoms always work as the catalytically active centers, decreasing the particle size of the catalyst can greatly boost the specific activity per metal atom. Single‐atom catalysts (SACs), containing single metal atoms anchored on supports, represent the utmost utilization of metallic catalysts and thus maximize the usage efficiency of metal atom. However, with the decreasing of particle size, the surface free energy increases obviously, and tends to aggregate into clusters or particles. Selection of an appropriate support is necessary to interact with isolated atoms strongly, and thus prevents the movement and aggregation of isolated atoms, creating stable, finely dispersed active sites. Furthermore, with uniform single‐atom dispersion and well‐defined configuration, SACs afford great space for optimizing high selectivity and activity. In this review, a detailed discussion of preparing, characterizing, and catalytically testing within this family is provided, including the theoretical understanding of key aspects of SACs materials. The main advantages of SACs as catalysts and the challenges faced for further improving catalytic performance are also highlighted.

Modular optimization of metal-organic frameworks (MOFs) was realized by incorporation of coordinatively unsaturated single atoms in a MOF matrix. The newly developed MOF can selectively capture and photoreduce CO with high efficiency under visible-light irradiation. Mechanistic investigation reveals that the presence of single Co atoms in the MOF can greatly boost the electron-hole separation efficiency in porphyrin units. Directional migration of photogenerated excitons from porphyrin to catalytic Co centers was witnessed, thereby achieving supply of long-lived electrons for the reduction of CO molecules adsorbed on Co centers. As a direct result, porphyrin MOF comprising atomically dispersed catalytic centers exhibits significantly enhanced photocatalytic conversion of CO , which is equivalent to a 3.13-fold improvement in CO evolution rate (200.6 μmol g h ) and a 5.93-fold enhancement in CH generation rate (36.67 μmol g h ) compared to the parent MOF.

Through a facile and effective strategy by employing lithium molten salts the controlled synthesis of 2H- and 1T-MoS monolayers with high-yield production is achieved. Both phases of MoS monolayers exhibit high stabilities. When used as a catalyst for hydrogen evolution, these phased MoS monolayers deliver respective advantages in the field of electro- and photo-catalytic hydrogen evolution.

Exploring novel functional materials is of vital importance in the development of science and technology, and thus beneficial to our daily life. Metal-organic frameworks (MOFs) and their composites as well as derivatives, with high porosity and tailorable chemical components, have drawn increasing interest in gas storage, energy conversion, and environment remediation in the past decades. This review highlights recent achievements on applications of MOF-based materials in the renewable energy and environmental science. Specifically, the developments and advantages of MOF-based materials are first presented and discussed. We then focus on the fabrication strategies of MOF-based materials and their applications in areas including gas adsorption, energy conversion, and storage. The well-established findings provide an indepth understanding for the construction and application of these advanced materials. This review concludes with some outlooks for the fields of energy conversion and environmental science by using MOF-based materials.

Constructing atomically dispersed platinum (Pt) electrocatalysts is essential to build high-performance and costeffective electrochemical water-splitting systems. We present a novel strategy to realize the traction and stabilization of isolated Pt atoms in the nitrogen-containing porous carbon matrix (Pt@PCM). In comparison with the commercial Pt/C catalyst (20 weight %), the as-prepared Pt@PCM catalyst exhibits significantly boosted mass activity (up to 25 times) for hydrogen evolution reaction. Results of extended x-ray absorption fine structure investigation and density functional theory calculation suggest that the active sites are associated with the lattice-confined Pt centers and the activated carbon (C)/nitrogen (N) atoms at the adjacency of the isolated Pt centers. This strategy may provide insights into constructing highly efficient single-atom catalysts for different energy-related applications.

Water splitting represents a promising technology for renewable energy conversion and storage, but it is greatly hindered by the kinetically sluggish oxygen evolution reaction (OER). Here, using Au-nanoparticle-decorated Ni(OH)2 nanosheets [Ni(OH)2-Au] as catalysts, we demonstrate that the photon-induced surface plasmon resonance (SPR) excitation on Au nanoparticles could significantly activate the OER catalysis, specifically achieving a more than 4-fold enhanced activity and meanwhile affording a markedly decreased overpotential of 270 mV at the current density of 10 mA cm(-2) and a small Tafel slope of 35 mV dec(-1) (no iR-correction), which is much better than those of the benchmark IrO2 and RuO2, as well as most Ni-based OER catalysts reported to date. The synergy of the enhanced generation of Ni(III/IV) active species and the improved charge transfer, both induced by hot-electron excitation on Au nanoparticles, is proposed to account for such a markedly increased activity. The SPR-enhanced OER catalysis could also be observed over cobalt oxide (CoO)-Au and iron oxy-hydroxide (FeOOH)-Au catalysts, suggesting the generality of this strategy. These findings highlight the possibility of activating OER catalysis by plasmonic excitation and could open new avenues toward the design of more-energy-efficient catalytic water oxidation systems with the assistance of light energy.

Graphitic carbon nitride (g‐C3N4) has recently emerged as an attractive photocatalyst for solar energy conversion. However, the photocatalytic activities of g‐C3N4 remain moderate because of the insufficient solar‐light absorption and the fast electron–hole recombination. Here, defect‐modified g‐C3N4 (DCN) photocatalysts, which are easily prepared under mild conditions and show much extended light absorption with band gaps decreased from 2.75 to 2.00 eV, are reported. More importantly, cyano terminal CN groups, acting as electron acceptors, are introduced into the DCN sheet edge, which endows the DCN with both n‐ and p‐type conductivities, consequently giving rise to the generation of p–n homojunctions. This homojunction structure is demonstrated to be highly efficient in charge transfer and separation, and results in a fivefold enhanced photocatalytic H2 evolution activity. The findings deepen the understanding on the defect‐related issues of g‐C3N4‐based materials. Additionally, the ability to build homojunction structures by the defect‐induced self‐functionalization presents a promising strategy to realize precise band engineering of g‐C3N4 and related polymer semiconductors for more efficient solar energy conversion applications.

Low efficiency and poor stability are two major challenges we encounter in the exploration of non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) in both acidic and alkaline environment. Herein, the hybrid of cobalt encapsulated by N, B codoped ultrathin carbon cages (Co@BCN) is first introduced as a highly active and durable nonprecious metal electrocatalysts for HER, which is constructed by a bottom-up approach using metal organic frameworks (MOFs) as precursor and self-sacrificing template. The optimized catalyst exhibited remarkable electrocatalytic performance for hydrogen production from both both acidic and alkaline media. Stability investigation reveals the overcoating of carbon cages can effectively avoid the corrosion and oxidation of the catalyst under extreme acidic and alkaline environment. Electrochemical active surface area (EASA) evaluation and density functional theory (DFT) calculations revealed that the synergetic effect between the encapsulated cobalt nanoparticle and the N, B codoped carbon shell played the fundamental role in the superior HER catalytic performance.