Confinement of sulfur-doped NiO nanoparticles into N-doped carbon nanotube/nanofiber-coupled hierarchical branched superstructures: Electronic modulation by anion doping boosts oxygen evolution electrocatalysis

The search for non-precious and efficient electrocatalysts towards the oxygen evolution reaction (OER) is of vital importance for the future advancement of multifarious renewable energy conversion/storage technologies. Electronic modulation via heteroatom doping is recognized as one of the most forceful leverages to enhance the electrocatalytic activity. Herein, we demonstrate a delicate strategy for the in-situ confinement of S-doped NiO nanoparticles into N-doped carbon nanotube/nanofiber-coupled hierarchical branched superstructures (labeled as S-NiO@N-C NT/NFs). The developed strategy simultaneously combines enhanced thermodynamics via electronic regulation with accelerated kinetics via nanoarchitectonics. The S-doping into NiO lattice and the 1D/1D-integrated hierarchical branched carbon substrate confer the resultant S-NiO@N-C NT/NFs with regulated electronic configuration, enriched oxygen vacancies, convenient mass diffusion pathways and superior architectural robustness. Thereby, the SNiO@N-C NT/NFs display outstanding OER properties with an overpotential of 277 mV at 10 mA cm(-2) and impressive long-term durability in KOH medium. Density functional theory (DFT) calculations further corroborate that introducing S-dopant significantly enhances the interaction with key oxygenate intermediates and narrow the band gap. More encouragingly, a rechargeable Zn-air battery using an air-cathode of Pt/C + S-NiO@N-C NT/NFs exhibits a lower charge voltage and preferable cycling stability in comparison with the commercial Pt/C + RuO2 counterpart. This study highlighting the concurrent consideration of electronic regulation, architectural design and nanocarbon hybridization may shed light on the future exploration of economical and efficient electrocatalysts. (C) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

The study demonstrates a method for in-situ confinement of S-doped NiO nanoparticles into N-doped carbon nanotube/nanofiber-coupled hierarchical branched superstructures. The resulting S-NiO@N-C NT/NFs exhibit outstanding OER performance and long-term durability, shedding light on the future exploration of economical and efficient electrocatalysts.