Embedding ultrasmall Ru nanoparticle catalytic sites on Ni₃Fe encapsulated carbon nanotubes for efficient and durable...

The rational design of high-efficiency, low-loading Ru-based heterogeneous catalysts represents a promising strategy for advancing hydrogen production via electrochemical water splitting. Herein, a heterogeneous electrocatalyst was constructed through in situ reduction of ultra-small Ru nanoparticles on the surface of Ni₃Fe alloy-encapsulated, N-doped carbon nanotubes (Ni₃Fe/N-CNTs) derived from a NiFe-layered double hydroxide (LDH) precursor. The as-synthesized Ru-Ni₃Fe/N-CNT catalyst exhibits exceptional activity and stability for the hydrogen evolution reaction (HER), requiring only an overpotential of 25 mV and a Tafel slope of 28.1 mV dec^-1 at 10 mA cm^-2. Furthermore, it maintains stable performance for over 100 h at 50 mA cm^-2 without obvious activity attenuation. This outstanding performance is attributed to the strong electronic coupling between the Ru nanoparticles, the Ni₃Fe alloy, and the N-CNT support, which collectively optimizes the reaction pathway and enhances structural stability. Additionally, the assembled Ru-Ni₃Fe/N-CNT//Ni₃Fe/N-CNT cell requires only1.58 V to achieve 20 mA cm^-2 for overall water splitting. Comprehensive structural characterization, surface property and theoretical calculations collectively reveal that the inner Ni₃Fe alloy and outer Ru induce charge redistribution, superhydrophilicity and electron coupling that not only optimizing the adsorption energy of H intermediates (ΔG_H) but also facilitating the H₂ desorption that can effectively improve the HER performance. The effective synergy between intrinsic electronic modulation and extrinsic nano structural engineering demonstrated in this study provides a viable avenue for the development of high-performance and cost-effective HER electrocatalysts.