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Fe–NC with Fe–N4–O1 active sites exhibits splendid catalytic activity toward the selective oxidation of amines. A possible mechanism combining the oxidative pathway and ROS pathway in the presence of Fe–NC is proposed.

The introduction of atomically dispersed Fe atoms can modulate the PMS activation pathway; that is, the radical-mediated process of PMS activation accelerated by graphitic N is attenuated, in turn boosting electron-transfer-mediated nonradical processes.

The obtained NiFe LDH/V–Co4N@NF shows strong electronic interaction at the heterointerface, which remarkably boosts its OER performance.

Peroxydisulfate (PDS) can be activated by graphitic carbon nitride (g-C3N4) under irradiation, and the generated oxygen reactive species (ROSs) can degrade organic pollutants effectively. However, the photocatalytic activity of pristine g-C3N4 is limited due to its narrow light absorption range and rapid electron–hole recombination. Herein, cobalt and phosphorus co-doped g-C3N4 (Co, P-CN) was synthesized by a facile one-pot pyrolysis method. Co and P co-doping enhances the light absorption and charge separation, thus greatly promoting the photocatalytic activation of PDS. Additionally, the presence of doped Co2+ can chemically activate PDS, with Co2+ transforming into Co3+ simultaneously. Recycling tests reveal that Co2+ in Co, P-CN can maintain a high level attributing to the fast Co3+/Co2+ transformation rate under light irradiation. The density functional theory (DFT) calculations show that the Co–Nx species formed by chemical coordination between Co and g-C3N4 in Co, P-CN could effectively activate PDS. The synergistic effect of photo-catalytic and chemical-catalytic driven PDS activation and a faster Co3+/Co2+ redox cycle result in the enhanced bisphenol A (BPA) degradation with a reaction rate constant (k) of 0.375 min−1, which is 7 times larger than that of pristine g-C3N4. This work provides an effective method for the in situ regeneration of active low-valent transition metal ions, and reveals the mechanism of synergistic activation of PDS by photo-catalysis and chemical-catalysis for pollutant degradation.

Persulfate-based advanced oxidation processes are promising technologies to solve water pollution. In this work, single iron atoms are anchored on three-dimensional N-doped carbon nanosheets by a chemical vapor deposition (CVD) method with ferrocene-loaded CaO as the hard template. The high surface density of Fe–N4 sites and abundant interconnected meso–macro pores are highly favorable for activating peroxymonosulfate (PMS) to produce superoxide radicals (O2˙−), giving rise to ultrahigh activity and excellent stability for pollutant degradation. Experiment and density functional theory (DFT) calculations reveal that Fe–N4 is the main active site, on which electrons transfer from C to Fe via the C–N–Fe bond to secure the low-valence state of Fe species for the redox process. This work proposes a new strategy for developing highly active single-atom materials by CVD and reveals mechanisms of PMS activation on single-atom activators.

Constructing two dimensional (2D) van der Waals (vdW) heterostructures is a promising strategy to overcome the shortcomings of individual 2D materials without losing their intrinsic advantages. This review first summarizes the different synthetic strategies for 2D heterostructures. The significant role of 2D heterointerfaces for energy storage and conversion is then discussed, involving charge transfer and redistribution, the 2D space-confined effect and the tunable 2D channel. The recent progress of 2D vdW heterostructures for energy-related electrochemical applications is reviewed, including electrocatalysts (e.g., hydrogen/oxygen evolution reaction and overall water splitting), Li+/Na+ ion batteries and supercapacitors. Advanced studies that highlight the impressive interfacial synergistic effect for improved performance are systematically introduced. Finally, current challenges and prospective solutions of this field for energy-related applications are proposed.

Herein, ultra-small molybdenum carbide nanodots encapsulated in nitrogen-doped porous carbon (Mo2C/N-PC) were synthesized by a facile one-pot method. Ammonium molybdate and low-cost starch were used as precursors of Mo2C and C. Ammonium nitrate was selected as a nitrogen dopant, which played multiple roles in the reduction of MoC to Mo2C, nitrogen doping of carbon, and formation of a porous structure with abundant structural defects, thus avoiding the high-temperature reduction by H2/Ar. The optimized Mo2C/N-PC hybrid has a remarkable catalytic activity towards the HER over a wide pH range (0–14). Especially, under alkaline conditions, an overpotential as small as −100 mV vs. RHE could be achieved at 10 mA cm−2, comparable to that of the best Mo2C-based materials. The density functional theory (DFT) calculations revealed that a decreased Gibbs free energy for H* adsorption (ΔGH*) could be obtained by combining Mo2C with N-PC, proving the synergistic enhancement mechanism of nitrogen doping and structural defects. This material contains no noble metals and can be easily synthesized on a large scale; thus, it should have significant potential in hydrogen production.

Metal-free carbon quantum dots (CQDs) have attracted great interest, but the rapid preparation of doped CQDs with tunable optical properties is still an urgent task. Herein, we report that covalent organic frameworks (covalent triazine-based frameworks, CTF-1) with layered structures can be rapidly exfoliated and cut into N-doped CQDs. The cutting mechanism involves triazine hydrolysis and breaking the bonds between the triazines and benzene rings. Experiments and density functional theory (DFT) calculations confirm that the fluorescence of the obtained CQDs mainly originates from the intrinsic state emission induced by localized π–π* transitions, despite the contribution of the defect state emission. Due to their unique chemical structure, the CQDs could be further utilized as an efficient PL probe for detecting Hg2+. This study may open up new avenues for developing new kinds of CQDs using covalent organic frameworks as the starting materials.

Recycling anode graphite remains a significant barrier to the recovery of used Li-ion batteries. In this study, we show that anode graphite in used lithium-ion batteries is a cheap and ideal candidate for the high yield production of high-quality graphene. Attributed to the reduced interlayer force after repeated charge–discharge cycles, the sonication assisted exfoliation efficiency of the used anode graphite can be 3 to 11 times that of natural graphite, with a highest mass yield of the dispersed graphene sheets of ∼40 wt%. Importantly, the layer numbers of most of the exfoliated graphene sheets are 1–4 , and their lateral sizes are over 1 μm. Their conductivity after annealing at moderate temperature (500 °C) is up to 9100 S m−1, and their potential application in conductive ink was also demonstrated.

In this study, we develop a facile strategy to combine an organic amine with a palladium complex on graphene oxide (GO) as a cooperative catalyst for Tsuji–Trost allylation. A tertiary amine and palladium–diamine complex are simultaneously immobilized on a GO support through silylation and further in situ coordination processes. PdCl2 is employed as the palladium precursor, with no necessity for extra coordination ligands. Various characterizations confirm the successful preparation of the cooperative supported catalyst (GO–NEt2–2N–Pd). Systematic investigation reveals the immobilized palladium–diamine complex (GO–2N–Pd) with very low Pd loading is effective for Tsuji–Trost allylation, and incorporation of the tertiary amine shows a significant promoting effect towards the catalytic activity. GO–NEt2–2N–Pd can be readily recovered and recycled several times without reduction of its efficiency. Its excellent performance should be ascribed to synergistic catalysis effect, excellent support properties, and robust immobilization interaction.

Graphene oxide (GO) is a promising support for anchoring homogeneous metal complexes because of its two-dimensional structure, huge surface area and diversity for chemical functionalizations. In this study, a ruthenium supported catalyst has been synthesized by covalently bonding a ruthenium complex (RuCl2(PPh3)3) onto the GO surface through coordination interaction with aminosilane ligand spacers. The supported catalyst showed enhanced catalytic performance towards hydrogenation of olefins and ketones compared with the homogeneous analogue, and it could be readily recycled and reused several times without discernible loss of its activity.