Nickel‐Foam‐ and Carbon‐Nanotubes‐Fiber‐Supported Bismuth Oxide/Nickel Oxide Composite; Highly Active and Stable Bifunctional Electrocatalysts for Water Splitting in Neutral and Alkaline Media

To increase the effectiveness of both the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER), significant efforts are made to produce bifunctional water‐splitting electrocatalysts. In this study, bismuth oxide/nickel oxide (Bi 2 O 3 /NiO)‐based composite is supported over the nickel foam (Bi 2 O 3 /NiO‐NF) and carbon nanotube fiber (Bi 2 O 3 /NiO‐CNTF) to develop two different electrode systems for water‐splitting studies. For OER, Bi 2 O 3 /NiO‐NF and Bi 2 O 3 /NiO‐CNTF require overpotential of 401 and 369 mV, respectively, to achieve the current density of 50 mA cm −2 in alkaline media, while the current density of 50 mA cm −2 is achieved at overpotential of 398 and 304 mV, respectively, in neutral media. For HER, Bi 2 O 3 /NiO‐NF and Bi 2 O 3 /NiO‐CNTF achieve the current density of 50 mA cm −2 at overpotential of 301 and 268 mV, respectively, in neutral media. For overall water splitting in neutral media, Bi 2 O 3 /NiO‐CNTF achieves the current density of 50 mA cm −2 at cell voltage of 1.654 V. The promising performance of synthesized electrocatalysts reveals that the mixed metal oxides (p‐block and d‐block elements)‐based electrocatalysts can be potential candidates for practical water splitting in basic (1 M KOH) as well as neutral media (1 M phosphate‐buffered saline).