Reduced Graphene Oxide/O-MWCNT Hybrids Functionalized with p‑Phenylenediamine as High-Performance MoS₂ Electrocatalyst Support for Hydrogen Evolution Reaction

Efficient hydrogen evolution through water splitting at low overpotentials is crucial to develop renewable energy technology, which depends on the design of efficient and durable electrocatalysts composed of earth-abundant elements. Herein, a highly and stable electrocatalyst for hydrogen evolution reaction (HER) has been developed on the basis of MoS₂ on p-phenylenediamine (PPD)-functionalized reduced graphene oxide/O-containing carbon nanotubes (rGO/O-MWCNT) hybrids via facile and green hydrothermal process. Among the prepared catalysts, the optimized MoS₂/rGO/PPD/O-MWCNT with nanosized and highly dispersed MoS₂ sheets provides a large amount of available edge sites and the improved electron transfer in 3D conductive networks. It exhibits excellent HER activity with a low overpotential of 90 mV and large current density of 47.6 mA·cm^–2 at 200 mV, as well as excellent stability in an acidic medium. The Tafel slope of 48 mV·dec^–1 reveals the Volmer–Heyrovsky mechanism for HER. Thus, this work paves a potential pathway for designing efficient MoS₂-based electrocatalysts for HER by functionalized conductive substrates

Co-Doped MoS₂ Nanosheets with the Dominant CoMoS Phase Coated on Carbon as an Excellent Electrocatalyst for Hydrogen Evolution

Highly active and low-cost catalysts for hydrogen evolution reaction (HER) are crucial for the development of efficient water splitting. Molybdenum disulfide (MoS₂) nanosheets possess unique physical and chemical properties, which make them promising candidates for HER. Herein, we reported a facile, effective, and scalable strategy by a deposition–precipitation method to fabricate metal-doped (Fe, Co, Ni) molybdenum sulfide with a few layers on carbon black as noble metal–free electrocatalysts for HER. The CoMoS phase after thermal annealing in Co-doped MoS₂ plays a crucial role for the enhanced HER. The optimized Co-doped MoS₂ catalyst shows superior HER performance with a high exchange current density of 0.03 mA·cm^–2, low onset potential of 90 mV, and small Tafel slope of 50 mV·dec^–1, which also exhibits excellent stability of 10000 cycles with negligible loss of the cathodic current. The superior HER activity originates from the synergistically structural and electronic modulations between MoS₂ and Co ions, abundant defects in the active edge sites, as well as the good balance between active sites and electronic conductivity. Thanks to their ease of synthesis, low cost, and high activity, the Co-doped MoS₂ catalysts appear to be promising HER catalysts for electrochemical water splitting

Metallic Cobalt Encapsulated in Bamboo-Like and Nitrogen-Rich Carbonitride Nanotubes for Hydrogen Evolution Reaction

Despite being technically possible, the hydrogen production by means of electrocatalytic water splitting is still practically unreachable mainly because of the lack of inexpensive and high active catalysts. Herein, a novel and facile approach by melamine polymerization, exfoliation and Co²⁺-assisted thermal annealing is developed to fabricate Co nanoparticles embedded in bamboo-like and nitrogen-rich carbonitride nanotubes (Co@NCN). The electronic interaction between the embedded Co nanoparticles and N-rich carbonitride nanotubes could strongly promote the HER performance. The optimized Co@NCN-800 exhibits outstanding HER activity with an onset potential of −89 mV (vs RHE), a large exchange current density of 62.2 μA cm^–2, and small Tafel slope of 82 mV dec^–1, as well as excellent stability (5000 cycles) in acid media, demonstrating the potential for the replacement of Pt-based catalysts. Control experiments reveal that the superior performance should be ascribed to the synergistic effects between embedded Co nanoparticles and N-rich carbonitride nanotubes, which originate from the high pyridinic N content, fast charge transfer rate from Co particles to electrodes via electronic coupling, and porous and bamboo-like carbonitride nanotubes for more active sites in HER