In situ electrochemical activation as a generic strategy for promoting the electrocatalytic hydrogen evolution reaction and alcohol electro-oxidation in alkaline medium.

In situ electrochemical activation as a new pre-treatment method is extremely effective for enhanced electrocatalytic performances for different applications. With the help of this method, in situ surface modification of electrocatalyst is achieved without using pre-made seeds or complex synthesis procedure. Herein, with the purpose of finding an in situ and simple electrochemical activation protocol, the green synthesis of Au/Pd nanoparticles (AuPd) by means of polyoxometalate (POM) is reported. Structural analysis of the AuPd nanohybrid unveil the Au-core/Pd-shell structure which surrounded by POM. We propose a novel cathodic electrochemical activation in phosphate buffer solution which can greatly boost the electrocatalytic activity of the as-prepared AuPd and Pd electrocatalyst not only for hydrogen evolution reaction (HER) as a model of electro-reduction, but also for methanol and ethanol electro-oxidation reaction (MOR & EOR). For the HER in 1 M NaOH solution, after the electrochemical activation, the needed potential to drive a geometrical current density of 10 mA cm-2 significantly decreases from - 400 mV vs. the reversible hydrogen electrode (RHE) to -290 mV vs. RHE. For the EOR and MOR, electrochemically activated AuPd realized 3.4- and 2.9- fold increase in mass current density (mA mgPd -1) with respect to the pristine AuPd electrocatalyst, respectively.

Efficient tetracycline adsorptive removal using tricaprylmethylammonium chloride conjugated chitosan hydrogel beads: Mechanism, kinetic, isotherms and thermodynamic study.

In the present study, novel ionic liquid-impregnated chitosan hydrogel beads (CS-TCMA) were fabricated via the reaction of tricaprylmethylammonium chloride (TCMA, Aliquat-336) with the chitosan's amino groups. They were used for the fast adsorption of Tetracycline (TC), as a pharmaceutical compound model, from aqueous solution. It was found that the impregnation of TCMA greatly improved the adsorption behaviour of chitosan toward TC. The optimum adsorbent was determined to be 3 mg/ L in a wide pH range of 5-11. It was a fast process, with a 90% removal efficiency in <45 min. The adsorption kinetic of TC on the CS-TCMA was well described by the pseudo-first-order model and intra-particle diffusion model. The adsorption also obeyed the Langmuir adsorption isotherm model and the maximum adsorption capacity obtained was 22.42 mg/g at 45 °C. The thermodynamic study also revealed the endothermic nature of the process. The adsorption mechanism was also studied.

A one-pot route for the synthesis of Au@Pd/PMo12/rGO as a dual functional electrocatalyst for ethanol electro-oxidation and hydrogen evolution reaction.

An in situ one-pot synthetic route for the synthesis of a Au@Pd/PMo12/reduced graphene oxide (rGO) nanocomposite is presented, where the Keggin-type polyoxometalate phosphomolybdic acid (PMo12) is used as both reducing and stabilizing agent. High-angle annular dark-field scanning transmission electron microscopy (HAADT-STEM), transmission electron microscopy (TEM), and X-ray diffraction analysis were applied to fully characterize the core-shell structure of Au@Pd/PMo12 on the rGO matrix. Electrochemical studies showed how this nanocomposite acts as a dual electrocatalyst for the ethanol electro-oxidation reaction (EOR) and the hydrogen evolution reaction (HER). For the EOR, the Au@Pd/PMo12/rGO electrocatalyst offers a low onset potential of -0.77 V vs. Ag/AgCl and a high peak current density of 41 mA cm-2 in alkaline medium. This feature is discussed via detailed cyclic voltammetry (CV) studies illustrating how the superior performance of the synthetic nanocomposite could be attributed to the synergistic effect of Au, Pd, PMo12 and rGO. Moreover, it has been confirmed that the proposed electrocatalyst exhibits low overpotentials for 10 mA cm-2 current density (η 10) in different pH media. The values of η 10 were -109, 300 and 250 mV vs. RHE in acidic, basic and neutral media, respectively. Also, the ability of the electrocatalyst to provide high HER current density and its remarkable stability have been confirmed.