NiCo alloy catalysts on nitrogen-doped carbon nanotubes split water efficiently

Researchers have developed a nickel–cobalt alloy catalyst supported on nitrogen-doped carbon nanotubes that can drive both halves of the water-splitting reaction, offering a potential route to hydrogen production without precious metals. The study, published in Advanced Composites and Hybrid Materials, reports that the optimised material requires low overpotentials to deliver a practical current density in both the oxygen evolution reaction and the hydrogen evolution reaction.

The team, led by Yufeng Hao and colleagues, first synthesised a microflower-like nickel–cobalt layered double hydroxide through a hydrothermal method. This precursor was then converted by calcination into NiCo alloy nanoparticles anchored on nitrogen-doped carbon nanotubes, a material the authors designate NiCo@NCNTs. By precisely controlling the amount of cobalt doping during synthesis, they produced a series of samples with tunable nickel-to-cobalt molar ratios, allowing them to identify the composition with the best catalytic performance.

Electrochemical testing showed that the optimal NiCo@NCNT catalyst achieved an overpotential of 295 millivolts for the oxygen evolution reaction and 255 millivolts for the hydrogen evolution reaction, each at a current density of 10 milliamperes per square centimetre. The corresponding Tafel slopes were 78 millivolts per decade for the oxygen evolution reaction and 116 millivolts per decade for the hydrogen evolution reaction, values that characterise how rapidly the reaction kinetics accelerate with applied voltage.

To test the material under realistic operating conditions, the researchers assembled the catalyst into a two-electrode water electrolyzer, using it for both the anode and cathode reactions. The device required a cell voltage of 1.70 volts to drive a current density of 10 milliamperes per square centimetre and maintained stable operation for more than 50 hours, an indication of durability under continuous electrolysis.

Theoretical calculations provided insight into why the alloy composition performs well. According to the study, incorporating cobalt into the nickel lattice modulates the electronic structure and strengthens synergistic interactions that adsorb and stabilise reaction intermediates. This, the authors report, accelerates the reaction kinetics and lowers the energy barriers for both the hydrogen and oxygen evolution reactions.

The calculations also pointed to a role for the interface between the alloy and the carbon nanotube support. Electronic reconstruction at the alloy–NCNT interface was found to modulate the nickel and cobalt electronic states, reducing the adsorption free energy of hydrogen and of oxygen-containing intermediates. In practical terms, the support is not merely a conductive scaffold but actively tunes the chemistry of the metal particles it anchors.

The motivation behind the work lies in the search for highly active, earth-abundant and stable bifunctional electrocatalysts.

As with any laboratory-scale electrochemical study, the reported overpotentials, cell voltage and 50-hour stability test describe performance under the specific conditions of the experiment, and further work would be needed to establish commercial viability. Nevertheless, the combination of tunable alloy composition, a nitrogen-doped carbon nanotube support and a detailed computational account of the electronic effects offers a coherent design strategy for non-precious-metal water-splitting catalysts.

Subject of Research: Bifunctional NiCo alloy electrocatalysts on nitrogen-doped carbon nanotubes for overall water splitting

Article Title: NiCo alloys anchored on N-doped carbon nanotubes as efficient bifunctional electrocatalysts for overall water splitting

Article References: Hao, Y., Zhou, H., Zhou, H., Zhang, Y., Qiao, Y., Meng, C., Yuan, A., Jiang, Y., & Zhang, Q. (2026). NiCo alloys anchored on N-doped carbon nanotubes as efficient bifunctional electrocatalysts for overall water splitting. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02130-w

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02130-w

Keywords: water splitting, electrocatalysis, NiCo alloys, nitrogen-doped carbon nanotubes, hydrogen evolution reaction, oxygen evolution reaction, overpotential, Tafel slope, layered double hydroxide, electrolyzer, hydrogen production, electronic structure