Production of a new 3D electrode skeleton of Ni with very high electrochemical surface area for oxygen evolution

Long and stable fibers (Tapes) of nickel with a thickness that can reach less than one hundred nanometers were produced through directional solidification of Ni-Al hypereutectic alloy on the surface of Ni and then, leaching the alloy in potassium hydroxide solution. Experimental results illustrated that the structure of the tapes is Raney nickel. In other words, a 3D structure consisting of a large number of Nano-dimensional tapes with a Nano-porous and Nano-crystalline structure was created. The activity of this structure was evaluated for oxygen evolution in alkaline media. The results showed that by increasing the number of Tapes per 〖cm〗^2 (density of Tapes), electrochemical surface area and double layer capacitance increase. As the density of Tapes increases, the OER overpotential decreases, but with further increase in density of Tapes, the OER overpotential increases again. Re-increase in overpotential was associated to trapping of oxygen bubbles. The best sample showed an overpotential 240 mV at 10 mA/〖cm〗^2 and 350 mV at 500 mA/〖cm〗^2. Also, this sample worked without any sign of degradation at 500 mA/〖cm〗^2 for 6 days (144 hours).

Membrane-Less Ethanol Electrooxidation over Pd-M (M: Sn, Mo and Re) Bimetallic Catalysts

The effect of the addition of three oxophilic co-metals (Sn, Mo and Re) on the electrochemical performance of Pd in the ethanol oxidation reaction (EOR) was investigated by performing half-cell and membrane-less electrolysis cell experiments. While the additions of Sn and Re were found to improve significantly the EOR performance of Pd, Mo produced no significant promotional effect. When added in significant amounts (50:50 ratio), Sn and Re produced a 3–4 fold increase in the mass-normalized oxidation peak current as compared to the monometallic Pd/C material. Both the electrochemical surface area and the onset potential also improved upon addition of Sn and Re, although this effect was more evident for Sn. Cyclic voltammetry (CV) measurements revealed a higher ability of Sn for accommodating OH- species as compared to Re, which could explain these results. Additional tests were carried out in a membrane-less electrolysis system. Pd50Re50/C and Pd50Sn50/C both showed higher activity than Pd/C in this system. Chronopotentiometric measurements at constant current were carried out to test the stability of both catalysts in the absence of a membrane. Pd50Sn50/C was significantly more stable than Pd50Re50/C, which showed a rapid increase in the potential with time. Despite operating in the absence of a membrane, both catalysts generated a high-purity (e.g., 99.99%) hydrogen stream at high intensities and low voltages. These conditions could lead to significant energy consumption savings compared to commercial water electrolyzers.

Preferential Protection of Low Coordinated Sites in Pt Nanoparticles for Enhancing Durability of Pt/C Catalyst

Protecting low coordinated sites (LCS) of Pt nanoparticles, which are vulnerable to dissolution, may be an ideal solution for enhancing the durability of polymer electrolyte fuel cells (PEMFCs). However, the selective protection of LCSs without deactivating the other sites presents a key challenge. Herein, we report the preferential protection of LCSs with a thiol derivative having a silane functional group, (3-mercaptopropyl) triethoxysilane (MPTES). MPTES preferentially adsorbs on the LCSs and is converted to a silica framework, providing robust masking of the LCSs. With the preferential protection, the initial oxygen reduction reaction (ORR) activity is marginally reduced by 8% in spite of the initial electrochemical surface area (ECSA) loss of 30%. The protected Pt/C catalyst shows an ECSA loss of 5.6% and an ORR half-wave potential loss of 5 mV after 30,000 voltage cycles between 0.6 and 1.0 V, corresponding to a 6.7- and 2.6-fold durability improvement compared to unprotected Pt/C, respectively. The preferential protection of the vulnerable LCSs provides a practical solution for PEMFC stability due to its simplicity and high efficacy.

Carbon-coated Single-phase Ti4O7 Nanoparticles as Electrocatalyst Support

The unique structure of Magnéli phases TiOx renders them effective for the electrochemical applications. This work demonstrates a synthesis of carbon-coated Magnéli phases TiOx (TiOx@C) nanoparticles from 3-aminophenol and rutile titania (TiO2) nanoparticles as a support for platinum (Pt) electrocatalyst. 3-aminophenol was polymerized and carbonized on the surface of TiO2 nanoparticles respectively in a microwave hydrothermal reactor and a tubular furnace. Reduction of the carbon-coated TiO2 (TiO2@C) into TiOx@C was performed in hydrogen atmosphere at 800-1050 °C. The carbon coating effectively prevented TiO2 nanoparticles from sintering, resulted in TiOx@C sizes from 50 to 100 nm. Single-phase Ti4O7 core, which has the highest theoretical electrical conductivity among the Magnéli phases, was obtained from reduction of TiO2@C at 1000 °C. for 10 min C/Ti4O7-supported Pt exhibited an electrochemical surface area of 46 m2 mgPt-1 at 15% Pt loading, slightly higher than that reported for commercial TKK electrocatalyst with 20% Pt loading (44.13 m2 mgPt-1).

Facilitating electrocatalytic hydrogen evolution via multifunctional tungsten@tungsten disulfide core–shell nanospheres

Multifunctional W@WS2 core–shell nanospheres with abundant catalytic sites, enhanced electrical conductivity, and enlarged electrochemical surface area for hydrogen evolution reaction.

Restructuring a gold nanocatalyst by electrochemical treatment to recover its H2 evolution catalytic activity

Oxidation–reduction recycling induces a restructuring of Au nanoparticles. Reconstructed Au nanoparticles have a clean surface and high electrochemical surface area and therefore, display high H2 evolution catalytic activities.