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.

The design and preparation of an excellent corrosion protection coating is still a grand challenge and is essential for large-scale practical application. Herein, a novel cationic reduced graphene oxide (denoted as RGO-ID)-based epoxy coating was fabricated for corrosion protection. RGO-ID was synthesized by in situ synthesis and salification reaction, which is stable dispersion in water and epoxy latex, and the self-aligned RGO-ID-reinforced cathodic electrophoretic epoxy nanocomposite coating (denoted as RGO-ID coating) at the surface of metal was prepared by electrodeposition. The self-alignment of RGO-ID in the coatings is mainly attributed to the electric field force. The significantly enhanced anticorrosion performance of RGO-ID coating is proved by a series of electrochemical measurements in different concentrated NaCl solutions and salt spray tests. This superior anticorrosion property benefits from the self-aligned RGO-ID nanosheets and the quaternary-N groups present in the RGO-ID nanocomposite coating. Interestingly, the RGO-ID also exhibits a high antibacterial activity toward Escherichia coli with 83.4 ± 1.3% antibacterial efficiency, which is attributed to the synergetic effects of RGO-ID and the electrostatic attraction and hydrogen bonding between RGO-ID and E. coli. This work offers new opportunities for the successful development of effective corrosion protection and self-antibacterial coatings.

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