Tailored heterostructured Ni₃N–NiO nano-frameworks for boosting electrocatalytic oxygen evolution via surface-modulated plasma strategy

The facile reconfiguration of phases plays a pivotal role in enhancing the electrocatalytic production of H₂ through heterostructure formation. While chemical methods have been explored extensively for this purpose, plasma-based techniques offer a promising avenue for achieving heterostructured nano-frameworks. However, the conventional plasma approach introduces complexities, leading to a multi-step fabrication process and challenges in precisely controlling partial surface structure modulation due to the intricate interaction environment. In our pursuit of heterostructures with optimized oxygen evolution reaction (OER) behavior, we have designed a facile auxiliary insulator-confined plasma system to directly attain a Ni₃N–NiO heterostructure (hNiNO). By meticulously controlling the surface heating process during plasma processing, such approach allows for the streamlined fabrication of hNiNO nano-frameworks. The resulting nano-framework exhibits outstanding catalytic performance, as evidenced by its overpotential of 320 mV at a current density of 10 mA·cm⁻², in an alkaline environment. This stands in stark contrast to the performance of NiO-covered Ni₃N fabricated using the conventional plasma method (sNiNO). Operando plasma diagnostics, coupled with numerical simulations, further substantiates the influence of surface heating due to auxiliary insulator confinement of the substrate on typical plasma parameters and the formation of the Ni₃N–NiO nanostructure, highlighting the pivotal role of controlled surface temperature in creating a high-performance heterostructured electrocatalyst.