Core–shell nanohybrids containing cheap inorganic nanocrystals and nanocarbon shells are promising electrocatalysts for water splitting or other renewable energy options. Despite that great progress has been achieved, biomimetic synthesis of metal phosphates@nanocarbon core–shell nanohybrids remains a challenge, and their use for electrocatalytic oxygen evolution reaction (OER) has not been explored. In this paper, novel nanohybrids composed of coralloid Co2P2O7 nanocrystal cores and thin porous nanocarbon shells are synthesized by combination of the structural merits of supramolecular polymer gels and a controllable thermal conversion technique, i.e., temperature programmable annealing of presynthesized supramolecular polymer gels that contain cobalt salt and phytic acid under a proper gas atmosphere. Electrocatalytic tests in alkaline solution show that such nanohybrids exhibit greatly enhanced electrocatalytic OER performance compared with that of Co2P2O7 nanostructure. At a current density of 10 mA cm–2, their overpotential is 0.397 V, which is much lower than that of Co2P2O7 nanostructures, amorphous Co-Pi nanomaterials, Co(PO3)2 nanosheets, Pt/C, and some reported OER catalysts, and close to that of commercial IrO2. Most importantly, both of their current density at the overpotential over 0.40 V and durability are superior to those of IrO2 catalyst. As revealed by a series of spectroscopic and electrochemical analyses, their enhanced electrocatalytic performance results from the presence of thin porous nanocarbon shells, which not only improve interfacial electron penetration or transfer dynamics but also vary the coordination environment and increase the number of active 5-coordinated Co2+ sites in Co2P2O7 cores.Keywords: carbon; cobalt phosphates; coordination environment and geometry; core−shell nanostructures; electrocatalysis; oxygen evolution reaction

Exploring low-cost, high-activity, and long-durability hybrid electrocatalysts for cathodic oxygen reduction reaction (ORR) is vital to advance fuel cells technologies. In this paper, a series of graphene (G)–CuxPdy (Cu4Pd, Cu3Pd, CuPd, CuPd3, CuPd4) nanocomposites (G–CuxPdy NCPs) is obtained by assembly of CuxPdy alloy nanocrystals (NCs) with controlled component ratios on G nanosheets using the “dispersing–mixing–vaporizing solvent” strategy and used as electrocatalysts for ORR. Compared with pure CuxPdy NCs, greatly enhanced interfacial electron transfer dynamics are observed in G–CuxPdy NCPs, which show a strong correlation with the alloy compositions of the NCPs. The electrocatalytic experiments in alkaline solution reveal that the ORR activities of those G–CuxPdy NCPs are also strongly dependent on alloy components and exhibit a double-volcano feature with variations of alloy components. Among them, G–Cu3Pd NCPs possess the highest electrocatalytic activity, which is much better than some reported electrocatalysts and commercial Pd/C catalyst and close to Pt/C catalyst. By correlating the Pd 3d binding energies and the sizes of CuxPdy NCs with the mass-specific activities of G–CuxPdy NCPs and considering the interfacial electron transfer dynamics, the best catalytic activity of G–Cu3Pd NCPs may result from the unique electronic structure and the smallest size of Cu3Pd NCs as well as the strong synergistic effect between G and Cu3Pd NCs. Moreover, the durability of G–Cu3Pd NCPs is superior to that of Pt/C catalyst, indicating that they are promising cathodic electrocatalysts for using in alkaline fuel cells.Keywords: assembly; bimetallic nanocrystals; electrocatalysis; graphene; nanocomposites; oxygen reduction reaction

In this paper, a series of well-coupled graphene (G) and MPd3 (M = Fe, Cu, Ag, Au, Cr, Mo, W) nanocrystals nanocomposites (G-MPd3 NCPs) have been synthesized via a versatile electrostatic assembly and hydrogen reduction strategy, i.e., sequential assembly of coordination anions and cations on excess cationic polymer modified graphene oxide to form composite precursors and then thermal treating under H2/Ar gases atmosphere. In those NCPs, the MPd3 components are uniform and smaller than 10 nm, which are well anchored on G with “naked” or “clean” surfaces. By adjusting reaction temperature, the interplay of MPd3 nanocrystals and G can be well-controlled. Below 700 °C, no sintering phenomena are observed, indicating the unprecedented dispersion and stability effect of G for MPd3 nanocrystals. All the obtained NCPs can be directly used to catalyze oxygen reduction reaction in alkaline media. Compared with single component, monometallic, and some reported non-Pt catalysts, greatly enhanced electrocatalytic performances are observed in those NCPs due to strong synergistic or coupling of their constituents. Among them, G-FePd3 NCPs exhibit the highest catalytic activity, but their current density needs to be improved compared with G-CrPd3, G-MoPd3, and G-WPd3 ones. This work not only provides a general strategy for fabricating well-coupled G-MPd3 NCPs but also paves the way for future designing multicomponent NCPs with multiple interfaces to apply in alkaline fuel cells.Keywords: bimetallic nanocrystals; electrocatalysis; electrostatic assembly; graphene; hydrogen reduction; nanocomposites;

This paper reports a simple method for immobilization of acetylcholinesterase (AChE) on one-dimensional (1D) gold (Au) nanoparticles for detection of organophosphorous (OP) insecticides. 1D Au nanoparticles were prepared by electrodeposition in the pores of an alumina template which was subsequently removed by 2.0 M NaOH solution. They were characterized by XRD and FESEM. The immobilized AChE retained its biological activity and catalyzed the hydrolysis of acetylthiocholine to form thiocholine, which was subsequently oxidized to produce detectable signals. Based on the inhibition toward the enzymatic activity of AChE by OP insecticides, sensitive detection of methamidophos (an OP insecticide) was performed. Under optimal conditions, the sensors could be used for the determination of methamidophos ranging from 0.004 to 24 μg/mL with the detection limit of 0.001 μg/mL. The developed OP insecticide biosensors exhibited satisfactory stability and reproducibility. This work demonstrated that 1D Au nanoparticles could serve as an ideal carrier for immobilization of AChE to fabricate the corresponding biosensor.