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The electrocatalytic activity of mixed Ru-Ir oxide electrodes fabricated by thermal decomposition are compared (using cyclic voltammetry and potentiodynamic technique), for their ability to evolve hydrogen and oxygen in both 1N H2SO4 and 1N NaOH solutions. Cyclic voltammetry provides information about the redox transitions of surface oxyruthenium and oxyiridium groups, and also generates an effective index, (voltammetric charge (q*)), which can be used to determine the electrocatalytic activity of the electrode. In this study, q* (obtained by numerical integration from CV), indicates that maximum activity results from a coating solution with 60 to 80 mol % Ir content. It is noted that, for acidic solutions, voltammetric charge in the region of hydrogen adsorption]desorption, (qn), exhibits the same trends as q*. The potentiodynamic technique, on the other hand, is employed to yield Tafel plots providing log(i) vs. E relations. It is found that the activity of RuO2 is worst for oxygen evolution in alkaline solutions, while its electrochemical behavior for hydrogen evolution is the same for both acidic and basic solutions. In contrast, it is found that the electrochemical behavior of IrO2 for hydrogen evolution is significantly influenced by pH.

Nanoporous carbon materials are a versatile source of carbons that would be useful in applications ranging from electronics to electrochemical energy storage. Here, we focus on nanoporous carbon materials prepared by direct carbonization of zeolitic imidazolate frameworks (ZIF-8) towards supercapacitor applications. Several types of nanoporous carbons have been prepared by varying the applied carbonization temperature. The symmetric devices assembled using nanoporous carbon electrodes were tested for their optimal performance in the electrolyte of sulfuric acid solution. We demonstrate the effects of various factors (e.g., surface area, nitrogen content, degree of graphitization, and relative percentage of micropores) on the performance.

The active sites of M0.1Ni0.9Co2O4 for the OER and ORR are successfully engineered for its application in rechargeable Zn–air batteries.

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