Metal–metal oxide nanostructure supported on graphene oxide as a multifunctional electro-catalyst for simultaneous detection of hydrazine and hydroxylamine

A ruthenium/iridium/iridium oxide nanohybrid supported on graphene oxide (RuIrOx_GO) was prepared via a new protocol. The activity of the nanohybrid towards the simultaneous detection of hydrazine (HY) and hydroxylamine (HA) was evaluated in phosphate-buffered saline solution (pH 7.0). Differential pulse voltammetry was used for the measurements, with a pulse amplitude of 50 mV and a scan rate of 0.04 V s−1. Using the modified electrode, the oxidation peak potentials for HY and HA can be easily distinguished, with a large peak separation of 0.36 V. Very low LOD values of 2.1 μM and 1.6 μM were found for HY and HA, respectively. The selectivity of the electrode and its stability were also studied The tolerance limits in the presence of different interfering compounds were evaluated. After five weeks, a deviation from the expected results of ~2% was observed for both HA and HY determinations. Keywords: Ir and Ru active phases, New synthesis protocol, Hydrazine, Hydroxylamine, Low detection limi

Active and stable graphene supporting trimetallic alloy-based electrocatalyst for hydrogen evolution by seawater splitting

The hydrogen evolution reaction (HER), adopting seawater as an electrolyte solution, is a promising and more sustainable alternative for the production of hydrogen, yet requiring more economic, highly efficient and stable electrocatalysts than the current ones. Herein, the synthesis of a Ni, Ru, Ir-based and graphene-supported nano-structured catalyst through an easily scalable, cost-effective, surfactant-free approach has been proposed. XRD, SEM, TEM images and EDX maps showed the formation of trimetallic NiRuIr alloy nanoparticles (average diameter: 8 nm) supported on a few-layer graphene. After characterization, the HER stability and activity of the sample were tested in a 0.5 M H2SO4, in a KCl neutral solution as well as in real seawater. In the acidic electrolyte environment a 0.06 V overpotential was maintained even after 11,000 cycles and the Tafel slope recorded was very low (28 mV/dec). In the neutral solution a very low overpotential (0.10 V) and a low Tafel slope (72 mV/dec) were also obtained. Furthermore, in real seawater the sample exhibits a Tafel slope of 48 mV/dec, maintains a low overpotential of 0.08 V for 250 cycles and a constant current density for 200 h of test without significant losses and with almost a 100% hydrogen production efficiency. The results obtained proved the remarkable HER performance of the synthesized electrocatalyst, especially in real seawater in virtue of synergistic alloying effects and the presence of the graphene support. Keywords: Trimetallic alloy, NiRuIr alloy, Seawater, Hydrogen evolution reaction, High stability, High H2 productio

Continuous flow HER evaluation of a new Pt-Pd/Conano-electrocatalyst

A new protocol of synthesis (e.g. choose of the solvent, precursors and amount and type of reducing agents) has been designed to prepare a Pt/Pd/Co alloy with a desired metals ratio. The stability of the alloy has been monitored after an acidic washing, to remove, if present, unalloyed metals and pre-leach the surface. An excellent combination of performance, e.g. Tafel slope lower than 30 mV/dec and a negligible overpotential, were measured for our Pt/Pd/Co NPs, with an atomic ratio (7:3:3) in a flow system. Very high hydrogen production rate of 7.09 mL cm−2h−1at −0.05 V was measured. The electrochemical production of hydrogen from liquid methanol in acidic solution was also investigated. The Pt/Pd/Co NPs exhibit an anodic current density of 560 mA/mgPtduring methanol oxidation in acidic solution at 0.45 V and an If/Ibratio of 1.96. A quantitative evaluation of the performance of the electrode in the two different processes has been made, too

High hydrogen production rate on RuS 2 @MoS 2 hybrid nanocatalyst by PEM electrolysis

A new nanocatalyst, which combines the electrocatalytic activity of MoS 2 nanosheets and RuS 2 nanoparticles (NPs), was prepared through a safe and scalable, one-step “bottom-up” approach. It delivers high current density, with a Tafel slope of 36 mV/dec and a very small overpotential. The high exposure of MoS 2 edges on the RuS 2 NPs, the stronger d character of RuS 2 and the electrical coupling of these two nanomaterials, grown together, were responsible for the high hydrogen production rates of 10.2 l/h (PEM cell 5cm × 5 cm, current density about 1.1 A/cm 2 , power consumption 41.8 W, corresponding to 3.8 KWh/Nm 3 of energy consumption, efficiency 93%)