Scrutinizing the electrocatalytic activity of ultra-low Pt- and Se-doped Ni nanoparticles/porous carbon electrocatalysts for tri-iodide reduction and urea oxidation

Surface reconstruction of electrocatalysts at the atomic scale is a powerful strategy to enhance catalytic performance by maximizing atomic utilization, modulating electronic structures, and generating highly active surface sites. In this work, ultra-low amounts of Pt and Se atoms were individually doped onto Ni nanoparticles embedded in a nitrogen-doped porous carbon (PC) matrix (denoted as Pt₁Ni/PC and Se_xNi/PC) via wet impregnation and surface adsorption methods. These atomic-level-modified catalysts were applied to the tri-iodide reduction reaction (IRR) and the urea oxidation reaction (UOR), demonstrating excellent catalytic activity and stability. For the IRR, both catalysts exhibited low charge transfer resistance (R_ct), resulting in high power conversion efficiencies in N719-based dye-sensitized solar cells (DSSCs). In the UOR, the catalysts achieved high current densities, low overpotentials, and small Tafel slopes, highlighting their fast reaction kinetics and superior electrocatalytic performance. Notably, a two-electrode system employing these catalysts delivered a current density of 50 mA cm⁻² at a low cell voltage of 1.57 V, which is approximately 0.22 V lower than that required for OER-driven water electrolysis (1.79 V). This performance underscores their promise for sustainable hydrogen production, direct urea fuel cells, and wastewater treatment applications. Density functional theory calculations further support the experimental findings, revealing that the atomic-level modification significantly enhances the electronic structure and catalytic activity of the Ni/PC framework.