Active and stable electrocatalysts made from earth-abundant elements are key to water splitting for hydrogen production through electrolysis. The growth of NiSe nanowire film on nickel foam (NiSe/NF) in situ by hydrothermal treatment of NF using NaHSe as Se source is presented. When used as a 3D oxygen evolution electrode, the NiSe/NF exhibits high activity with an overpotential of 270 mV required to achieve 20 mA cm(-2) and strong durability in 1.0 M KOH, and the NiOOH species formed at the NiSe surface serves as the actual catalytic site. The system is also highly efficient for catalyzing the hydrogen evolution reaction in basic media. This bifunctional electrode enables a high-performance alkaline water electrolyzer with 10 mA cm(-2) at a cell voltage of 1.63 V.
Nonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low-temperature fuel cells. A novel type of catalysts prepared by high-pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting of uniform iron carbide (Fe3 C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide-based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts.
Over the past few decades, direct methanol fuel cells (DMFCs) have been intensively developed as clean and high-efficiency energy conversion devices. However, their dependence on expensive Pt-based catalysts for both the anode and the cathode make them unsuitable for large-scale commercialisation. The essential solution to addressing this shortfall is the development of low-Pt and non-Pt catalysts. Regarding this issue, considerable advances have been made with low-Pt alloys and core-shell-like catalysts, as well as non-platinum Pd-Me, Ru-Se and heat-treated MeN x C y -based catalysts. This perspective reviews potential pathways for increasing the cost-effectiveness and efficiency of these catalysts. Fundamental understanding of the composition-activity and structure-activity relationships, innovative synthesis, and promising developmental directions are highlighted. Regarding durability, the main degradation mechanism of these catalysts and the corresponding mitigating strategies are presented.
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