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