Supercritical CO2-Assisted synthesis of NiFe2O4/vertically-aligned carbon nanotube arrays hybrid as a bifunctional electrocatalyst for efficient overall water splitting

Highly efficient and cost-effective bifunctional electrode materials are vital for both hydrogen and oxygen evolution reactions in water splitting. Assisting by the unique supercritical carbon dioxide (SC-CO2) technique, NiFe2O4 nanoparticles are directly anchored on the vertically aligned carbon nanotubes (VACNT). The integrated hybrid electrocatalyst of NiFe2O4/VACNT demonstrates remarkable catalytic activities for both OER and HER. It requires overpotentials of only 240 mV and 150 mV to achieve 10 mA cm(-2) anodic and cathodic current densities, respectively. Such excellent performance is credited to the synergistic effect raising from the interaction of tiny NiFe2O4 particles and VACNT, which provides highly exposed catalytic sites, fast charge transport, excellent reactant diffusion and interface infiltration. This work not only provides an effective technique to prepare efficient electrocatalyst for overall water splitting but also offers important understandings in nanostructure engineering for rational design functional materials in multidisciplinary application including energy conversion. (c) 2019 Elsevier Ltd. All rights reserved.