Suchergebnisse

Interface engineering is a powerful strategy for modulating electronic structure and enhancing intrinsic activity of electrocatalysts for water splitting. Here, we grow two-dimensional cobalt-iron hydroxide (CoFe-OH) nanosheets on nickel foam substrates and deposit FeOOH nanoparticles in a rapid and scalable wet chemical approach. The CoFe-OH@FeOOH nanocomposite features abundant active sites and high surface area, allowing fast kinetics for electrochemical water splitting. The electrode has a low overpotential value of 200 mV at 50 mA cm$^{−2}$ for oxygen evolution. When used as both anode and cathode for overall water splitting, CoFe-OH@FeOOH provides a low cell voltage of 1.56 V to deliver 10 mA cm$^{−2}$ current density. The synergistic activity is presumed to be from the seamless interface of CoFe-OH and FeOOH, improving conductivity and mass transfer. We envision that this simple approach may offer a new direction for designing efficient electrodes for energy conversion applications. ; This research was supported by the King Abdullah University of Science and Technology, Kingdom of Saudi Arabia, and by a Human Resources Development Program (20194030202470) of the Korea Institute of Energy Technology, Evaluation, and Planning (KETEP) grant funded by the Korean Government Ministry of Trade, Industry, and Energy, Republic of Korea.

Porous organic polymers with labile leaving groups offer direct access to reactive functional groups, otherwise not permissible during network formation. In a one-step, open air, self-coupling reaction of tris bromomethyl benzene, we report highly porous, bromine rich C–C bonded porous polymers. Due to the steric nature of the monomer, restrictive crosslinking allowed pendent bromine groups to remain unreacted and provided rapid exchange into amines, nitriles, and thiols. This simple but powerful strategy yielded two isostructural but varying porosity and pendent group density polymers, allowing a comparative gas uptake study. Despite having lower surface area, the porous polymer formed at low temperature showed higher amination due to higher density of bromine groups. The polymers with more pendant groups resulted better CO2 uptake performances than higher porosity polymers with less pendant groups. Although post-modification decreased surface area of materials, amine functionalization greatly improved the CO2 uptake capacity. The ethylenediamine appended version exhibited 4.7 times increase in CO2 uptake capacity with highest CO2/N2 selectivity of 729 (298 K), and with an isosteric heat of 97 kJ mol−1 at zero coverage. ; This work was supported by National Research Foundation of Korea (NRF) grants funded by the Korean government (MSIP) (No. NRF-2017M3A7B4042140 and NRF-2017M3A7B4042235) and the startup funds by the King Abdullah University of Science and Technology (KAUST).