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Molecular catalysts dispersed on nanocarbon substrates represent a unique class of single atom catalysts (SACs) for their well-defined active sites and tailorable structures, and are promising substitutes to precious metals for catalyzing the technologically important oxygen reduction reaction (ORR). Herein, we develop a highly active ORR catalyst consisting of iron phthalocyanine uniformly and densely dispersed on puff-like graphene (FePc/PG). With the unique crumpled and spheroid morphology, the graphene carrier possesses a large surface area and multiscale porosity, benefiting the high-density loading of FePc, exposure of the active sites and mass transfer efficiency during catalysis. When evaluated by a rotating disk electrode, FePc/PG presents a high half-wave potential of 0.909 V vs.the reversible hydrogen electrode. Furthermore, when employed as the gas diffusion electrode, FePc/PG exhibits outstanding high-rate and highpower capabilities at practically high current densities. This work provides efficient strategies to engineer the morphology of the nanocarbon substrates to design high-performance heterogeneous molecular catalysts toward applications in diverse energy conversion and storage technologies.

Direct seawater electrolysis is a promising technology for massive green hydrogen production but is limited by the lack of durable and efficient electrocatalysts toward the oxygen evolution reaction (OER). Herein, we develop a core–shell nanoreactor as a high-performance OER catalyst consisting of NiFe alloys encapsulated within defective graphene layers (NiFe@DG) by a facile microwave shocking strategy. This catalyst needs overpotentials of merely 218 and 276 mV in alkalized seawater to deliver current densities of 10 and 100 mA cm–2, respectively, and operates continuously for 2000 h with negligible activity decay (1.0%), making it one of the best OER catalysts reported to date. Detailed experimental and theoretical analyses reveal that the excellent durability of NiFe@DG originates from the formation of the built-in electric field triggered by the defective graphene coating against chloride ions at the electrode/electrolyte interface, thus protecting the active NiFe alloys at the core from dissolution and aggregation under harsh operation conditions. Further, a highly stable and efficient seawater electrolyzer is assembled with the NiFe@DG anode and the Pt/C cathode to demonstrate the practicability of the catalysts.

Metal- and nitrogen-coordinated nanocarbons (M-N/Cs) represent the most promising nonprecious catalysts for the oxygen reduction reaction (ORR), but it remains challenging to simultaneously achieve high intrinsic activity, fast mass transport, and efficient utilization of active sites in a single catalyst. Herein, we design an Fe-N/C catalyst consisting of edge-hosted Fe-N3sites dispersed on multiscale porous carbon frameworks (eFe-N3/PCF). The low coordination and edge effect of the Fe-N3moieties endow eFe-N3/PCF with high intrinsic activity, while the enriched nanopores enable improved mass transport and atom utilization efficiency. When evaluated by a rotating disk electrode in the base, eFe-N3/PCF presents early-onset and half-wave potentials of 1.090 and 0.934 V versus the reversible hydrogen electrode, respectively. Furthermore, when employed as gas diffusion electrodes, eFe-N3/PCF displays excellent mass-transport efficiency that enables high-rate/power capabilities at practically high current densities. This work opens up opportunities for designing high-performance ORR electrocatalysts toward applications in diverse energy conversion and storage technologies.

Two-dimensional tin monosulfide (SnS) is attractive for the development of electronic and optoelectronic devices with anisotropic characteristics. However, its shape-controlled synthesis with an atomic thickness and high quality remains challenging. Here, we show that highly crystalline SnS nanoribbons can be produced via high-pressure (0.5 GPa) and thermal treatment (400 °C). These SnS nanoribbons have a length of several tens of micrometers and a thickness down to 5.8 nm, giving an average aspect ratio of ∼30.6. The crystal orientation along the zigzag direction and the in-plane structural anisotropy of the SnS nanoribbons are identified by transmission electron microscopy and polarized Raman spectroscopy, respectively. An ionic liquid-gated field-effect transistor fabricated using the SnS nanoribbon exhibits an on/off current ratio of >103and a field-effect mobility of ∼0.7 cm2V–1s–1. This work provides a unique way to achieve one-dimensional growth of SnS.

Chemical vapor deposition (CVD) is a scalable method able to synthesize MoS2and WS2monolayers. In this work, we reduced the synthesis temperature by 200 °C only by introducing tellurium (Te) into the CVD process. The as-synthesized MoS2and WS2monolayers show high phase purity and crystallinity. The optical and electrical performance of these materials is comparable to those synthesized at higher temperatures. We believe this work will accelerate the industrial synthesis of these semiconducting monolayers.

Oxygen reduction and evolution reactions are essential for broad range of renewable energy technologies such as fuel cells, metal-air batteries and hydrogen production through water splitting, therefore, tremendous effort has been taken to develop excellent catalysts for these reactions. However, the development of cost-effective and efficient bifunctional catalysts for both reactions still remained a grand challenge. Herein, we report the electrocatalytic investigations of bamboo-shaped carbon nitrogen nanotubes (CNNTs) having different diameter distribution synthesized by liquid chemical vapor deposition technique using different nitrogen containing precursors. These CNNTs are found to be efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions. The electrocatalytic activity strongly depends on the nanotube diameter as well as nitrogen functionality type. The higher diameter CNNTs are more favorable for these reactions. The increase in nanotube diameter itself enhances the catalytic activity by lowering the oxygen adsorption energy, better conductivity, and further facilitates the reaction by increasing the percentage of catalytically active nitrogen moieties in CNNTs.

The scarcity and high cost of platinum-based electrocatalysts for the oxygen reduction reaction (ORR) has limited the commercial and scalable use of fuel cells. Heteroatom-doped nanocarbon materials have been demonstrated to be efficient alternative catalysts for ORR. Here, graphene quantum dots, synthesized from inexpensive and earth-abundant anthracite coal, were self-assembled on graphene by hydrothermal treatment to form hybrid nanoplatelets that were then codoped with nitrogen and boron by high-temperature annealing. This hybrid material combined the advantages of both components, such as abundant edges and doping sites, high electrical conductivity, and high surface area, which makes the resulting materials excellent oxygen reduction electrocatalysts with activity even higher than that of commercial Pt/C in alkaline media.

Recently, two-dimensional layers of transition metal dichalcogenides, such as MoS2, WS2, MoSe2, and WSe2, have attracted much attention for their potential applications in electronic and optoelectronic devices. The selenide analogues of MoS2and WS2have smaller band gaps and higher electron mobilities, making them more appropriate for practical devices. However, reports on scalable growth of high quality transition metal diselenide layers and studies of their properties have been limited. Here, we demonstrate the chemical vapor deposition (CVD) growth of uniform MoSe2monolayers under ambient pressure, resulting in large single crystalline islands. The photoluminescence intensity and peak position indicates a direct band gap of 1.5 eV for the MoSe2monolayers. A back-gated field effect transistor based on MoSe2monolayer shows n-type channel behavior with average mobility of 50 cm2V–1s–1, a value much higher than the 4–20 cm2V–1s–1reported for vapor phase grown MoS2.

The development of strategies for tuning the electronic structure of the metal sites in single-atom catalysts (SACs) is the key to optimizing their activity. Herein, we report that iodine doping within the carbon matrix of a cobalt–nitrogen–carbon (Co–N–C) catalyst can effectively modulate its electronic structure and catalytic activity toward the hydrogen evolution reaction (HER). The iodine-doped Co–N–C catalyst shows exceptional HER activity in acid with an overpotential of merely 52 mV at 10 mA cm–2, a small Tafel slope of 56.1 mV dec–1, making it among the best SACs based on both precious and nonprecious metals. Moreover, this catalyst possesses a high turnover frequency (TOF) value of 1.88 s–1(η = 100 mV), which is about 1 order of magnitude larger than that (0.2 s–1) of the iodine-free counterpart. Experimental and theoretical studies demonstrate that the introduction of iodine dopants lowers the chemical oxidation state of the Co sites, resulting in the optimized hydrogen adsorption and facilitated HER kinetics. This work provides an alternative strategy to regulate the electronic structure of SACs for improved performance.