A three-dimensional (3D) MoS2/CoS2 composite with shell/core heterostructure is in situ synthesized, which is composed of CoS2 acicular nanorod arrays and edge-terminated MoS2 nanosheets vertically grown on each CoS2 nanorod. Benefiting from the epitaxial growth of 2H-MoS2 on the surface of CoS2, the edge planes of ultrathin MoS2 nanosheets are significantly exposed. Due to the structural properties, a large number of direct contact areas are formed between MoS2 and CoS2, and a strong interaction between these two phases causes the electrons at the interface to be redistributed. Owing to the synergy of MoS2 and CoS2, significantly increased MoS2 edge sites, and improved mass transfer and electron transport, MoS2/CoS2 exhibits a remarkable catalytic ability for hydrogen evolution reaction (HER) at full pH. In 1.0 M KOH, 1 M PBS (pH = 7.0), and 0.5 M H2SO4, the overpotential at a current density of 10 mA cm–2 is 97, 196, and 126 mV, with Tafel slope of 78.7, 77.5, 42.6 mV dec–1, respectively. In addition to reporting a promising HER catalyst, this work will also provide a meaningful reference for designing 3D nanocatalysts.

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The carbons containing metals coordinated with nitrogen are emerging as the most promising catalysts toward various heterogeneous catalyses. In this paper, such a carbon catalyst is prepared through a chemical vapor deposition (CVD)‐supported precursor pyrolysis. Compared with the direct pyrolysis of polypyrrole@cobalt salt precursor, the incorporation of dicyanodiamide as the CVD source facilitates the diversification and hierarchization of carbon morphology, the reduction of Co particle size, and the increase of the proportion of interfacial Co−N−C and pyridinic‐N. The catalyst is composed of in‐situ‐grown multiple‐morphology carbons (MMCs) with metallic Co particles embedded, where the MMCs are a combination of nano‐particles, ‐rods, and ‐wires, all comprised by small N‐doped carbon nanoflakes. Owing to the combined modulation on morphology configurations and defect states, the Co/MMCs catalyst demonstrates excellent activities toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). A half‐wave potential of 0.84 V and low overpotentials of 86 and 180 mV at 10 mA cm−2 current density for HER and OER are achieved, respectively. Additionally, the catalyst also demonstrates favorable prospects for large‐scale applications in overall water splitting and Zn‐air battery.