Nickel on Oxidatively Modified Carbon as a Promising Cost-Efficient Catalyst for Reduction of P-Nitrophenol.

The reduction of p-nitrophenol to p-aminophenol has become a benchmark reaction for testing the efficiency of new catalytic systems. In this study, we use oxidatively modified carbon (OMC) as a structural support to develop a new cost-efficient nickel-based catalytic system. The newly developed material comprises single nickel ions, chemically bound to the oxygen functional groups on the OMC surface. The highly oxidized character of OMC ensures the high lateral density of nickel ions on its surface at relatively low nickel content. We demonstrate excellent catalytic properties of the new material by using it as a stationary phase in a prototype of a continuous flow reactor: the reagent fed into the reactor is p-nitrophenol, and the product, exiting the reactor, is the fully converted p-aminophenol. The catalytic properties of the new catalyst are associated with its specific morphology, and with high lateral density of active sites on the surface. The reaction can be considered as an example of single-atom catalysis. The resulting material can be used as an inexpensive but efficient catalyst for industrial wastewater treatment. The study opens the doors for the synthesis of a new series of catalytic systems comprising transition metal atoms on the OMC structural support.

A systematic computational study of the structure crossover and coordination number distribution of metallic nanoparticles.

In this study, we identified stable configurations for three nanoparticle structure motifs (icosahedral, decahedral and cuboctahedral) of eight transition metals (Cu, Ag, Au, Pd, Ni, Rh, Ir, and Pt) ranging in size from 140 to 3000 atoms. We made simple yet precise analytical approximations of the energy of the stable configurations as a function of nanoparticle size and calculated the structure crossover sizes from these approximations. We then analyzed the surface structure of the nanoparticles in terms of the distribution of the coordination numbers and active sites. We found that low-coordinated atoms are most preferable for cuboctahedral forms and for lighter metals - Cu, Ni and Rh. Compared to other considered metals, gold nanoparticles exhibited unique features as follows: the least amount of low-coordinated atoms, the largest fraction of (111) faces on its surface and a concave reconstruction of five-fold vertices.