NiO–Ni/CNT as an Efficient Hydrogen Electrode Catalyst for a Unitized Regenerative Alkaline Microfluidic Cell

Tailoring active, durable, and cost-effective electrocatalysts is crucial for hydrogen evolution (HER) and oxidation reactions (HOR) in an alkaline medium. Herein, the synthesis, physicochemical, and electrochemical characterization of NiO–Ni nanostructures supported on multiwalled carbon nanotubes (CNTs), as well as their performance in a unitized regenerative alkaline microfluidic cell (URAμFC) as a hydrogen bifunctional electrode are reported. The hydrogen electrode reaction (HER/HOR) activity on the NiO–Ni/CNT nanomaterial (0.36 mA cm–2) outperformed that of commercial Pd/C (0.05 mA cm–2) and turned out to be competitive with commercial Pt/C (0.56 mA cm–2). With the NiO–Ni/CNT catalyst, a maximum power density (fuel cell mode) of ca. 40 mW cm–2 was obtained, whereas the electrocatalyst subjected to the electrolyzer mode consumed an electrical power density of ca. 165 mW cm–2 at 100 mA cm–2.