The exploration of highly efficient and stable bifunctional electrocatalysts for overall water splitting is currently of extreme interest for the efficient conversion of sustainable energy sources. Herein, we provide an earth-abundant, low-cost, and highly efficient bifunctional electrocatalyst composed of cobalt sulfide (CoS) and molybdenum carbide (MoC) nanoparticles anchored to metal-organic frameworks (MOFs)-derived nitrogen, sulfur-codoped graphitic carbon (CoS-NSC@MoC). The new composite mode of the electrocatalyst was realized through simple pyrolysis processes. The composite electrocatalyst shows outstanding hydrogen evolution reaction (HER) performance and excellent stability over the entire pH range. For example, it has a lower overpotential of 74, 89, and 121 mV with the Tafel slopes of 69.3, 86.7, and 106.4 mV dec to achieve a current density of 10 mA cm in 0.5 M HSO, 1.0 M KOH, and 1.0 M phosphate-buffered saline solutions, respectively. Moreover, it shows a small overpotential of 293 mV with a Tafel slope of 59.7 mV dec to reach 10 mA cm for the oxygen evolution reaction (OER) in 1.0 M KOH. The significantly enhanced HER and OER activities of CoS-NSC@MoC are mainly attributable to the electron transfer from Co to MoC, resulting in a lower Mo valence and a higher Co valence in CoS-NSC@MoC. Furthermore, using the CoS-NSC@MoC bifunctional electrocatalyst as both the anode for the OER and the cathode for the HER for overall water splitting, a cell voltage of only 1.61 V is needed to derive a current density of 10 mA cm. This interesting work offers a general method for designing and fabricating highly efficient and stable non-noble electrocatalysts for promising energy conversion.

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Prevention of water, oxygen, and chloride ions contained in hydrotalcite interlayers from diffusing through the layered double hydroxides (LDH) is of crucial importance in corrosion protection. In this work, a hybrid composed of reduced graphene oxide (RGO) nanosheets/Zn/Al layered double hydroxide (RGO/ZnAl-LDH) composite films on the surface of 6N01 aluminum (Al) alloy was successfully synthesized by a novel and facile hydrothermal continuous flow method, which enabled direct growth of the composite on the surface of the Al alloy substrate. The structure and morphology of the RGO/ZnAl-LDH composite films were fully characterized. Based on electrochemical measurements in a NaCl solution, the RGO/ZnAl-LDH composite film significantly enhanced the corrosion protection, as compared with the ZnAl-LDH film. The RGO/ZnAl-LDH composite film could maintain an outstanding corrosion resistance after 7 days immersion in a high concentration of NaCl solution (i.e., 5.0 wt %). The enhanced corrosion resistance was attributed to the barrier effect on diffusion of water, oxygen, and chloride ions by the RGO contained in the RGO/ZnAl-LDH composite films.

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