Trace Ru-tuned NiO/CNT electrocatalysts outperform benchmark Pt for alkaline hydrogen evolution with superior mass activity

The exploitation of highly active and durable electrocatalysts that can replace high-cost Pt/C for hydrogen evolution reaction (HER) is urgently required. The challenge lies in diminishing the usage of noble metals without sacrificing HER activity. In this work, trace Ru-doped transition metal oxides (TMOs) nanoparticles (∼7 nm) with high dispersion loaded by the carbon nanotubes (CNTs) were developed. Specifically, Ru-NiO/CNTs with a low Ru content of 0.94 wt% exhibits excellent alkaline HER activity with the low overpotential of 19 mV and 98 mV to achieve the current density of 10 mA·cm−2 and 100 mA·cm−2, respectively, outperforming Ru/CNTs counterpart and most previously Ru-based nanocatalysts. Notably, the mass activity (1.83 A·mgRu-1) and price activity (301.51 A·dollar-1) of Ru-NiO/CNTs are separately more than 7 times and 18 times higher than that of the commercial 20% Pt/C benchmark. Moreover, the catalyst can operate without activity decay after 100 h long-term stability test. DFT calculation reveals that the synergy effects are originated from (i) the accelerated adsorption and dissociation of H2O by Ru, and (ii) the optimized electronic structure of Ni that tunes the H* adsorption/desorption. Furthermore, we discover that Ru-promoted HER activity shows a metal-dependent relationship (Ni ≈ Cu > Mn > Co > Fe), which can use binding energy shift (ΔE) as a highly correlated descriptor. This work may provide an insightful understanding of Ru dopant for enhanced HER activity.