Probing competent electrocatalysts for hydrogen evolution reaction (HER) of water splitting is one of the most hopeful approaches to confront the energy and environmental crisis. Herein, we highlight ultrathin N-doped MoC nanosheets (N-MoC NSs) in the role of greatly efficient platinum-free-based electrocatalysts for the HER. The transformation of crystal phase and structure between MoO nanosheets with a thickness of ∼1.1 nm and N-MoC NSs with a thickness of ∼1.0 nm is studied in detail. Structural analyses make clear that the surfaces of the N-MoC NSs are absolutely encompassed by apical Mo atoms, hence affording an ideal catalyst prototype to expose the role of Mo atoms for the duration of HER catalysis. Theoretical calculations demonstrate that the nanosheet structure, N doping, and particular crystalline phase of MoC produce more exposed Mo active sites, including Mo atoms on the C plane and doped N atoms. Through detailed electrochemical investigations, N-MoC NSs possess HER activity with an onset potential of -48.3 mV vs RHE, Tafel slope of 44.5 mV dec, and overpotential of 99 mV vs RHE at the cathodic current density of 10 mA cm with excellent long-term stability. Lastly, the calcination temperature and dicyandiamide amount can obviously affect the phase transformation and surface structure of molybdenum carbide, resulting in an adjustable HER activity. This synthesis mechanism will facilitate the understanding and optimization of Mo-based electrocatalysts in the energy conversion field.

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Acidic electrolytes are advantageous for water electrolysis in the production of hydrogen as there is a large supply of H(+) ions in the solution. In this study, with the applied overpotential larger than the equilibrium potential of Ni(0)/Ni(2+), Ni foam as HER electrode exhibits excellent and stable HER activity with an onset potential of -84 mV (vs RHE), a high current density of 10 mA cm(-2) at -210 mV (vs RHE), and prominent electrochemical durability (longer than 5 days) in acidic electrolyte. The results presented herein may has potential large-scale application in hydrogen energy production.

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The uptake of precious metals from electronic waste is of environmental significance and potential commercial value. A facile bioreductive synthesis is described for Au nanoparticles (ca. 20 nm) supported on N-doped carbon (Au@NC), which was derived from Au/Pycnoporus sanguineus cells. The interface and charge transport between Au and N-doped carbon were confirmed by HRTEM and XPS. Au@NC was employed as an electrocatalyst for the hydrogen evolution reaction (HER), exhibiting a small onset potential of -54.1 mV (vs. RHE), a Tafel slope of 76.8 mV dec(-1) , as well as robust stability in acidic medium. Au@NC is a multifunctional electrocatalyst, which demonstrates high catalytic activity in the oxygen reduction reaction (ORR), as evidenced by an onset potential of +0.97 V, excellent tolerance toward methanol, and long-term stability. This work exemplifies dual recovery of precious Au and fabrication of multifunctional electrocatalysts in an environmentally benign and application-oriented manner.

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