Metal-free phosphorus-doped graphene nanosheets (P-TRG) with large surface area (496.67 m 2 g 21 ) and relatively high P-doping level (1.16 at.%) were successfully prepared by thermal annealing a homogenous mixture of graphene oxide and 1-butyl-3-methlyimidazolium hexafluorophosphate under argon atmosphere. It was found that the P atoms were substitutionally incorporated into the carbon framework and were partially oxidized, which created new active sites for the oxygen reduction reaction (ORR).Accordingly, the ORR catalytic performance of the P-doped graphene was demonstrated to be better than or at least comparable to that of the benchmark Pt/C catalyst.

increasing interest since it exhibits a suppressed Fenton reactivity in comparison to Fe-N-C while maintains a remarkable catalytic activity. [18-20] To rationally design CoN -C catalyst for ORR, downsizing active species to single-atom scale and intentionally incorporating specific N into carbon matrix have been proposed to facilitate the catalytic process. [21-27] The former strategy can achieve a maximum atom-utilization efficiency and full exposure of active sites while the latter strategy usually involves pyridinic-N construction to optimize the charge distribution and improve the density of states at the Fermi level of the adjacent C atoms, facilitating the oxygen adsorption and reduction reaction. [28,29] For example, Yin et al. synthesized singleatom CoN x-C electrocatalyst through the pyrolysis of cobalt-coordinated framework porphyrin with graphene and found that it exhibited a high half-wave potential of 0.83 V, much better than Co nanoparticles-N-C electrocatalyst (0.73 V). [30] Han et al. investigated the size effect on the electrocatalytic activity of Co catalysts from nanometer to singleatom scale, demonstrating that cobalt single atoms on N-doped carbon could achieve a higher half-wave potential (0.82 V) and a larger limiting diffusion current density (4.96 mA cm −2) than atomic Co clusters (0.81 V, 4.44 mA cm −2) and Co nanoparticles counterpart (0.80 V, 3.86 mA cm −2). [31] Wang et al. developed a laser irradiation strategy to modulate the relative contents of pyridinic and pyrrolic nitrogen dopants in the electrocatalyst and reported that pyridinic-NCo bonding instead of pyrrolic-N bonding could optimize the adsorption energy of reaction intermediates in ORR process. [32] Despite prominent achievements that have been made recently, most studies on CoN -C catalysts focused on only one of the above-proposed strategies, and thus their catalytic performance is still unsatisfied to meet the practical application. Therefore, developing an effective synthetic strategy for the integration of generating atomically dispersed active sites and achieving pyridinic-N-optimized electronic structure to increase the catalytic activity of CoN -C catalyst is highly demanded but remains significant challenging. Herein, we have innovatively developed a highly effective lysozyme (Lys)-assisted metal-organic framework (MOF) approach to prepare single-atom Co implanted pyridinic-N doped porous carbon catalysts. During the pyrolysis process, the attached Lys on the surrounding of Co-ZIF-8 (zeolitic imidazolate frameworks) not only can effectively trap metal atoms Engineering transition metal-nitrogen-carbon (TM-N-C) catalysts with highdensity accessible active sites and optimized electronic structure holds great promise in the context of the electrochemical oxygen reduction reaction (ORR). Herein, a novel modification of a lysozyme-modified zeolitic imidazolate framework with isolated Co atoms anchored on dominated pyridinic-N doped carbon (Co-pyridinic N-C) is reported. The atomically dispersed Co allows the maximum ...

Developing a multifunctional electrocatalyst with eminent activity, strong durability, and cheapness for the hydrogen/oxygen evolution reaction (HER/OER) and oxygen reduction reaction (ORR) is critical to overall water splitting and regenerative fuel cells. Herein, a nitrogen-doped nanonetwork assembled by porous and defective NiCo2O4@C nanowires grown on nickel foam (N-NiCo2O4@C@NF) is crafted via biomimetic mineralization and following carbonization of phase-transited lysozyme (PTL)-coupled NiCo2O4. The as-obtained N-NiCo2O4@C@NF electrocatalysts exhibit an exceptional catalytic activity with ultralow overpotentials for the HER (42 mV) and OER (242 mV) to afford 10 mA cm–2 while maintaining good stability in alkaline media. Meanwhile, the N-NiCo2O4@C electrocatalysts presents a superior catalytic activity for ORR and a favorable four-electron pathway. The unprecedented catalytic performance arises from a highly porous structure and abundant defects and synergistic effects of components. This work may offer a new possibility in the exploration of multifunctional electrocatalysts for various energy-related electrocatalytic reactions.

Assembling metal-organic framework (MOF)-based particles is an emerging approach for creating colloidal superstructures and hierarchical functional materials. However, realization of this goal requires strategies that not only regulate particle interactions but also harness the anisotropic morphologies and functions of various frameworks. Here, by exploiting depletion interaction induced by ionic amphiphiles, we show the assembly of a broad range of low-dimensional MOF colloidal superstructures, including 1D straight chains, alternating or bundled chains, 2D films of hexagonal, square, centered rectangular, and snowflake-like architectures, and quasi-3D supercrystals. With well-defined polyhedral shapes, the MOF particles are mutually oriented upon assembly, producing super-frameworks with hierarchically coordinated crystallinity and micropores. We demonstrate this advantage by creating functional MOF films with optical anisotropy, in our cases, birefringence and anisotropic fluorescence. Given the variety of MOFs available, our technique should allow access to advanced materials for sensing, optics, and photonics.