Composition-Driven Synergistic Enhancement of NiCo Electrocatalysts for High-Efficiency Alkaline Overall Water Splitting

The development of inexpensive, highly efficient, and durable bifunctional electrocatalysts is crucial for large-scale hydrogen production through alkaline water splitting. NiCo-based catalysts have attracted significant interest due to their high catalytic activity and stability in alkaline solutions [1]. This study reports the fabrication of nickel-cobalt (Ni_xCo_y) bifunctional electrocatalysts with different compositions (Ni₉₆Co₄, Ni₉₀Co₁₀, Ni₈₀Co₂₀, Ni₅₀Co₅₀, and Ni₂₀Co₈₀) via electroless deposition on pretreated copper (Cu) substrates, where the Cu substrates were cleaned in HCl:H₂O (1:1, v/v) and activated in a 0.5 g L^-1 PdCl₂ solution before deposition. The morphology and composition of the catalysts were characterized using SEM, EDS, XRD, XPS, and ICP-OES. The electrocatalytic performance of the electrocatalysts toward HER and OER was evaluated in 1 M KOH using a three-electrode setup, while the OWS performance was assessed in a two-electrode system.

Among the catalysts, Ni₉₀Co₁₀/Cu exhibited the lowest overpotential of 94.8 mV at a current density of 10 mA cm^-2 at 25 °C, confirming its superior HER activity. Ni₅₀Co₅₀/Cu showed the lowest overpotential of 362.6 mV at a current density of 10 mA cm^-2 at 25 °C, indicating superior OER performance. An electrolyzer assembled with Ni₅₀Co₅₀/Cu as both the anode and cathode required a minimal voltage of 1.623 V to achieve a current density of 10 mA cm^-2, outperforming all other compositions evaluated for OWS. Moreover, Ni₅₀Co₅₀ exhibited excellent HER durability in 1 M KOH, showing only a slight potential shift from -0.0554 to -0.0567 V vs. RHE over 15 h of chronopotentiometric testing at -10 mA cm^-2. These results highlight the potential of Ni_xCo_y electrocatalysts for efficient overall water splitting and hydrogen production.

Reference:

Wang, X., Wang, T., Yu, Y., You, J., Hu, F., & Zhao, D. (2024). Enhancing the efficiency and stability of electrocatalysts for water splitting: NiCo-LDH nanosheet arrays at high current density. CrystEngComm, 26(37), 5144-5151.