Atomic Layer Deposition of NiOOH/Ni(OH)2 on PIM-1-Based N-Doped Carbon Nanofibers for Electrochemical Water Splitting in Alkaline Medium.

Portable and flexible energy devices demand lightweight and highly efficient catalytic materials for use in energy devices. An efficient water splitting electrocatalyst is considered an ideal future energy source. Well-aligned high-surface-area electrospun polymers of intrinsic microporosity (PIM-1)-based nitrogen-doped carbon nanofibers were prepared as a free-standing flexible electrode. A non-noble-metal catalyst NiOOH/Ni(OH)2 was precisely deposited over flexible free-standing carbon nanofibers by using atomic layer deposition (ALD). The morphology, high surface area, nitrogen doping, and Ni states synergistically showed a low onset potential (ηHER =-40 and ηOER =290 mV vs. reversible hydrogen electrode), small overpotential at η10 [oxygen evolution reaction (OER)=390.5 mV and hydrogen evolution reaction (HER)=-147 mV], excellent kinetics (Tafel slopes for OER=50 mV dec-1 and HER=41 mV dec-1 ), and high stability (>16 h) towards water splitting in an alkaline medium (0.1 m KOH). The performance was comparable with that of state-of-the-art noble-metal catalysts (e.g., Ir/C, Ru/C for OER, and Pt/C for HER). Post-catalytic characterization with X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy further proved the durability of the electrode. This study provides insight into the design of 1D-aligned N-doped PIM-1 electrospun carbon nanofibers as a flexible and free-standing NiOOH/Ni(OH)2 decorated electrode as a highly stable nanocatalyst for water splitting in an alkaline medium.