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An integrated and reproducible chemical process was developed to fabricate the N-doped mesoporous carbon by using melamine resin as nitrogen source. A two-dimensional carbon framework of graphene sheets was also used as a conductive substrate in order to boost the performance of such nitrogen-doped carbon materials. Compared with the pure mesoporous carbon, the as-made nitrogen-doped carbon/ graphene electrode materials exhibited suitable pore size distribution, ordered meso-structure, and uniformly dispersed N atoms with tunable doping amount. These unique properties make them promising electrodes for supercapacitors with superior performance. In particular, N-doped carbon and decorated graphene electrodes could deliver the specific capacitance of 238 and 289 F/g at the current density of 0.2 A/g in a three-electrode system. The results from symmetrical two-electrode revealed that the highly N-doped carbon electrodes offered excellent rate capability (ca. 78% retention as the current density increased from 0.1 to 20 A/g) and superior cycling performance (ca. 91% retention after 1000 cycles).

Low cost and green fabrication of high-performance electrocatalysts with earth-abundant resources for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial for the large-scale application of rechargeable Zn–air batteries (ZABs). In this work, our density functional theory calculations on the electrocatalyst suggest that the rational construction of interfacial structure can induce local charge redistribution, improve the electronic conductivity and enhance the catalyst stability. In order to realize such a structure, we spatially immobilize heterogeneous CoS/CoO nanocrystals onto N-doped graphene to synthesize a bifunctional electrocatalyst (CoS/CoO@NGNs). The optimization of the composition, interfacial structure and conductivity of the electrocatalyst is conducted to achieve bifunctional catalytic activity and deliver outstanding efficiency and stability for both ORR and OER. The aqueous ZAB with the as-prepared CoS/CoO@NGNs cathode displays a high maximum power density of 137.8 mW cm−2, a specific capacity of 723.9 mAh g−1 and excellent cycling stability (continuous operating for 100 h) with a high round-trip efficiency. In addition, the assembled quasi-solid-state ZAB also exhibits outstanding mechanical flexibility besides high battery performances, showing great potential for applications in flexible and wearable electronic devices.

A coordination-assisted pyrolysis procedure was adopted to encapsulate palladium (Pd) nanoparticles in a mesoporous carbonaceous matrix. X-ray diffraction and transmission electron microscopy measurements revealed that approximately 2.5 nm nanoparticles were highly dispersed inside the well-ordered porous framework. High-resolution TEM and temperature-programmed hydride decomposition analysis demonstrated the formation of interstitial carbon in the Pd lattice. Diffuse reflectance infrared Fourier transform spectroscopy indicated that carbon species could be deposited on low-coordinated surface sites of the Pd particles. This catalyst exhibited high activity in the selective hydrogenation of cinnamaldehyde (CAL) at 80 °C under an H2 pressure of 1.0 MPa (turnover frequency (TOF) of 2.4 s–1) to produce hydrocinnamyl aldehyde with high selectivity (HCAL; approximately 80%) in water and could be reused eight times with no clear activity loss. A trapping agent poisoning experiment using solid SH-SBA-15 revealed unobvious leaching of Pd into the solution. Exposure to thiourea with a S:Pd ratio of 0.1 resulted in slight activity and undetectable selectivity losses over the current catalyst in the selective hydrogenation of CAL at 80 °C under an H2 pressure of 1.0 MPa. However, a 50% activity loss was observed for commercial Pd/C. Even after an increase in the thiourea concentration to a S:Pd ratio of 3, the TOF remained at 1.9 s–1 with a negligible effect on the HCAL selectivity. Nearly complete deactivation of Pd/C occurred upon high exposure to thiourea. DFT calculations showed that the presence of surface or subsurface carbon can enhance the poison tolerance of the encapsulated Pd catalysts. The enhanced hydrogenation activity and strong poison tolerance are consistent with the interpretation that Pd nanoparticles are modified by carbonaceous deposits.

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