Atomically dispersed Pt-N-4 sites as efficient and selective electrocatalysts for the chlorine evolution reaction

Chlorine evolution reaction (CER) is a critical anode reaction in chlor-alkali electrolysis. Although precious metal-based mixed metal oxides (MMOs) have been widely used as CER catalysts, they suffer from the concomitant generation of oxygen during the CER. Herein, we demonstrate that atomically dispersed Pt-N-4 sites doped on a carbon nanotube (Pt-1/CNT) can catalyse the CER with excellent activity and selectivity. The Pt-1/CNT catalyst shows superior CER activity to a Pt nanoparticle-based catalyst and a commercial Ru/Ir-based MMO catalyst. Notably, Pt-1/CNT exhibits near 100% CER selectivity even in acidic media, with low Cl- concentrations (0.1M), as well as in neutral media, whereas the MMO catalyst shows substantially lower CER selectivity. In situ electrochemical X-ray absorption spectroscopy reveals the direct adsorption of Cl- on Pt-N-4 sites during the CER. Density functional theory calculations suggest the PtN4C12 site as the most plausible active site structure for the CER

Oxygen reduction catalysed by carbon supported iridium-chelates

Carbon supported iridium-octaethylporphyrin (IrOEP), iridium-tetraphenylporphyrin (IrTPP) and iridium-phthalocyanine (IrPc) were studied in acid for the oxygen redn. Both porphyrins give a four-electron redn., although a peculiar deactivation at low potentials occurs. At IrPc and heat-treated porphyrins hydrogen peroxide is formed. Results are compared with carbon monoxide oxidn. expts. at these catalysts. A single site mechanism is proposed for the oxygen redn. mechanism. [on SciFinder (R)

Mesoporous carbons supported non-noble metal Fe-NX electrocatalysts for PEM Fuel Cell oxygen reduction reaction

Three types of iron-nitrogen containing non-noble metal catalysts, supported on an ultrasonic spray pyrolysis mesoporous carbon (USPMC), a hollow core mesoporous shell carbon (HCMSC), and a standard carbon (Ketjen Black CJ600, KB), respectively, are synthesized using a wet-impregnation method. The morphologies and structure as well as composition of the synthesized carbon supports and their corresponding supported Fe-NX catalysts (namely Fe-NX/USPMC, Fe-NX/HCMSC, and Fe-NX/KB, respectively) are physically characterized using EDX, SEM, FESEM, and BET analysis, respectively. The catalytic activities of these three electrocatalysts towards oxygen reduction reaction (ORR) are measured using rotating disk electrode technique in O2-saturated 0.5 M H2SO4 solution. The catalyzed ORR exchange current densities are also obtained using the Tafel method based on the measured data. Among these three electrocatalysts, Fe-NX/HCMSC can give the best ORR performance, which is correlated to its higher nitrogen, mesopore and micropore contents. It is rationalized that the performance improvement of these electrocatalysts may be achieved as long as an optimal relationship among mesopores, micropores, and even macropores for increasing both ORR kinetics and reactant gases accessibility to the active sites can be foun