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Herein, we report a facile and environment-friendly route for the preparation of Co9S8 activated N/S co-doped carbon tubes (denoted as Co9S8@N/S–CT) in situ grown on a carbon nanofiber network derived from bacterial cellulose. The as-prepared Co9S8@N/S–CT has a novel microstructure with homogeneous and lotus root-like carbon tubes plugged with Co9S8 active substance, which are embedded in the carbon nanofibers. This nonprecious Co9S8@N/S–CT composite has a comparable catalytic activity for the oxygen reduction reaction and superior stability compared with commercial Pt/C catalyst. This is attributed to a synergistic catalytic effect due the intimate contact between Co9S8 active sites and the highly conductive heteroatom doped carbon tubes, showing the great potential for using the Co9S8@N/S–CT composite as a novel non-precious cathode catalyst in fuel cells or metal–air battery applications.

High-performance and low-cost bifunctional electrocatalysts play crucial roles in oxygen reduction and evolution reactions. Herein, a novel three-dimensional (3D) bifunctional electrocatalyst was prepared by embedding CoO nanoparticles into nitrogen and sulfur co-doped carbon nanofiber networks (denoted as CoO@N/S-CNF) through a facile approach. The carbon nanofiber networks were derived from a nanostructured biological material which provided abundant functional groups to nucleate and anchor nanoparticles while retaining its interconnected 3D porous structure. The composite possesses a high specific surface area and graphitization degree, which favors both mass transport and charge transfer for electrochemical reaction. The CoO@N/S-CNF not only exhibits highly efficient catalytic activity towards oxygen reduction reaction (ORR) in alkaline media with an onset potential of about 0.84 V, but also shows better stability and stronger resistance to methanol than Pt/C. Furthermore, it only needs an overpotential of 1.55 V to achieve a current density of 10 mA cm−2, suggesting that it is an efficient electrocatalyst for oxygen evolution reaction (OER). The ΔE value (oxygen electrode activity parameter) of CoO@N/S-CNF is calculated to be 0.828 V, which demonstrates that the composite could be a promising bifunctional electrocatalyst for both ORR and OER.

Electrocatalysts play a vital role in electrochemical water-splitting for hydrogen production. Here, we report the preparation of three-dimensional molybdenum phosphide (MoP) as a non-precious-metal electrocatalyst for the hydrogen evolution reaction (HER) by using cheap sponge (polyurethane, PU) as a sacrificial template. The obtained 3D MoP not only has large surface area, but also possesses a porous and channel-rich structure, in which the side walls of the pores are composed of refined nanoparticles. The 3D MoP sponge was used as a bulky and binder-free HER electrode and exhibited excellent catalytic activity in an acidic electrolyte (achieving 10 and 20 mA cm−2 at an overpotential of 105 and 155 mV, respectively). In addition, this novel bulky HER electrode showed a relatively small Tafel slope of 126 mV dec−1, a high exchange current density of 3.052 mA cm−2, and a faradaic efficiency of nearly 100%. Furthermore, this bulky electrode revealed high tolerance and durability both under acidic and basic conditions, maintaining 96% and 93% of its initial catalytic activity after continuous testing for 60 000 s. Thus, our work paves a feasible way of fabricating a cheap and highly efficient HER electrode on a large-scale for electrochemical water-splitting technology.