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To explore low-cost, high-efficiency, and noble-metal-free catalysts for electrocatalytic water splitting in both acidic and alkaline media, the metal-metal carbide Janus hierarchical structure comprising Mo and β-Mo2C embedded on a carbon layer (Mo/β-Mo2C)@C is synthesized by a hydrothermal reaction and subsequent low-temperature magnesium thermic process. Systematic characterization by XRD, XPS, Raman scattering, and SEM/TEM reveals the successful formation of metallic Mo and β-Mo2C nanoparticles. The synthesized (Mo/β-Mo2C)@C has a large specific surface area and boasts highly efficient hydrogen evolution reaction activity including low overpotentials of 152 mV and 171 mV at a current density of 10 mA cm-2 and small Tafel slopes of 51.7 and 63.5 mV dec-1 in acidic and alkaline media, respectively. In addition, the catalyst shows outstanding stability for 48 hours in both acidic and alkaline media. The excellent catalytic activity originates from more active sites and greater electron conductivity bestowed by the carbon layer, which also improves the long-term stability in both acidic and alkaline solutions.

The tribological behaviors of Cu-based bulk metallic glass (BMG) Cu50.2Zr40.8Ti8.5Nb0.5 and conventional nickel-aluminum bronze (NAB) reference material were investigated in air and in 3.5% NaCl solution, respectively. The tribology tests were performed at room temperature using a reciprocating tribo-meter at a sliding speed of 1 m min−1 against 6 mm diameter ZrO2 ball. When sliding in air, the friction coefficient of Cu-based BMG decreases with the applied loads (5 N, 10 N and 20 N) and the wear behavior mainly affected by abrasion, delamination and oxidation. In particularly, the wear rate of Cu-based BMG is about 22 times lower than that of conventional NAB when sliding in air under a load of 5 N. When sliding in 3.5wt.% NaCl solution, Cu-based BMG demonstrates better static-corrosion resistance but worse tribo-corrosion resistance comparing with conventional NAB. Compared with the corresponding wear in air, the wear rate of the BMG in 3.5% NaCl solution increases at 5 N, but decreases at 20 N due to the combined effects of corrosion and lubrication caused by solution. The tribocorrosion of Cu-based BMG is mainly controlled by abrasive wear and the synergistic effects of abrasion and corrosion. By applying -1.3 V cathodic potential, the corrosive wear rate of Cu-based BMG at 5 N was reduced by nearly 50%. This work provides an experimental reference for the tribological evaluation of Cu-based BMG in different environments.