Rational construction of ultrafine noble metals onto carbon nanoribbons with efficient oxygen reduction in practical alkaline fuel cell

Abstract In pursuit of sustainable and eco-friendly energy output, fuel cells are well-recognized as the most promising candidates in clean energy conversion and storage technology. Noble metal-based nanomaterials have long been regarded as the most efficient electrocatalysts for the oxygen reduction reaction (ORR) in terms of activity, selectivity, and stability. Here, we propose a self-template strategy where a type of hexagonal tubular InOF-25 could be tuned by adding a different amount of surfactants. Owing to the suitable pore size, these fabricated X-CTAB@InOF-25 (X = 50–300) series are used as precursors to encapsulate a series of discrete metal complexes, including Ag(NH3)2+, AuCl4-, PdCl42-, and PtCl62-. Then, the as-prepared carbon nanoribbons doped with precious metals (M@CNR, M = Pd, Pt, Ag, Au) exhibit good performance in the electrocatalytic ORR as well as Zn-air battery due to their large surface area, rich active sites, and extremely active noble metal nanoparticles. Among them, the most optimal Pd@CNR shows an onset potential of 0.94 V vs. RHE, high diffusion-limited current density of 5.87 mA cm-2, small Tafel slope of 51.74 mV dec-1, and satisfying stability with current retention of 95.4% after 10 h. Meanwhile, these obtained M@CNR as cathode catalysts are modeled and proved by the theoretical calculation with strong oxygen adsorption for efficient ORR. In this context, the main issues, large overpotential required for ORR and fast degradation of the electrocatalysts, impair practical application, which could be relieved by the active noble metals well-protected by carbon nanomaterials from the rational design and preparation of precursors.