Atomic layer deposition of Pd nanoparticles on self-supported carbon-Ni/NiO-Pd nanofiber electrodes for electrochemical hydrogen and oxygen evolution reactions

[Display omitted] •Self-supported CNF-Ni/NiO-Pd electrodes were fabricated.•Electrospinning with atomic layer deposition were used for the electrode fabrication.•CNF-Ni/NiO-Pd electrodes were used for HER and OER reactions under acidic and basic conditions.•CNF-Ni/NiO-Pd electrodes have shown high HER and OER activity compared to Pt and IrO2 catalysts.•Synergistic effect between the graphitic nanosheets, Ni/NiO and Pd NPs at the nanointerfaces has been highlighted. The most critical challenge in hydrogen fuel production is to develop efficient, eco-friendly, low-cost electrocatalysts for water splitting. In this study, self-supported carbon nanofiber (CNF) electrodes decorated with nickel/nickel oxide (Ni/NiO) and palladium (Pd) nanoparticles (NPs) were prepared by combining electrospinning, peroxidation, and thermal carbonation with atomic layer deposition (ALD), and then employed for hydrogen evolution and oxygen evolution reactions (HER/OER). The best CNF-Ni/NiO-Pd electrode displayed the lowest overpotential (63 mV and 1.6 V at j = 10 mA cm−2), a remarkably small Tafel slope (72 and 272 mV dec−1), and consequent exchange current density (1.15 and 22.4 mA cm−2) during HER and OER, respectively. The high chemical stability and improved electrocatalytic performance of the prepared electrodes can be explained by CNF functionalization via Ni/NiO NP encapsulation, the formation of graphitic layers that cover and protect the Ni/NiO NPs from corrosion, and ALD of Pd NPs at the surface of the self-supported CNF-Ni/NiO electrodes.