S, N Dual-Doped Graphene-like Carbon Nanosheets as Efficient Oxygen Reduction Reaction Electrocatalysts

Replacement of rare and precious metal catalysts with low-cost and earth-abundant ones is currently among the major goals of sustainable chemistry. Herein, we report the synthesis of S, N dual-doped graphene-like carbon nanosheets via a simple pyrolysis of a mixture of melamine and dibenzyl sulfide as efficient metal-free electrocatalysts for oxygen reduction reaction (ORR). The S, N dual-doped graphene-like carbon nanosheets show enhanced activity toward ORR as compared with mono-doped counterparts, and excellent durability in contrast to the conventional Pt/C electrocatalyst in both alkaline and acidic media. A high content of graphitic-N and pyridinic-N is necessary for ORR electrocatalysis in the graphene-like carbon nanosheets, but an appropriate amount of S atoms further contributes to the improvement of ORR activity. Superior ORR performance from the as-prepared S, N dual-doped graphene-like carbon nanosheets implies great promises in practical applications in energy devices

Improving Electrocatalysts for Oxygen Evolution Using Ni_<i>x</i>Fe_3–<i>x</i>O₄/Ni Hybrid Nanostructures Formed by Solvothermal Synthesis

Spinel-type oxides have been found to be active electrocatalysts for OER. However, their semiconductor character severely limits their catalytic performance. Herein, we report a facile solvothermal pathway for the synthesis of spinel-type Ni_<i>x</i>Fe_3–<i>x</i>O₄ oxides/Ni metal nanocomposites. The good electrical contact between the metal and semiconductor oxide interface and well-tuned compositions of Ni_<i>x</i>Fe_3–<i>x</i>O₄ spinel oxides are crucial to achieve better OER performance. Specifically, the Ni_<i>x</i>Fe_3–<i>x</i>O₄/Ni nanocomposite sample prepared from a metal precursor ratio of <i>y</i> = 0.15 [<i>y</i> = Fe/(Fe + Ni)] that results in an <i>x</i> value of about 0.36 exhibits catalytic activity with an overpotential of 225 mV to achieve an electrocatalytic current density of <i>j</i> = 10 mA cm^–2 and a Tafel slope of 44 mV dec^–1 in alkaline electrolyte. This study not only provides new perspectives to designing nanocomposite catalysts for OER but also opens a promising avenue for further enhancing electrocatalytic performance via interface and composition engineering