Nanoporous modified Ni₃Sn₄ intermetallics nanoarrays for enhanced alkaline hydrogen evolution catalysts

A stepwise fabrication strategy is developed to construct high-surface-area Ni-rich nanoporous layer covered Ni₃Sn₄ intermetallic nanoarrays. This process involves surface alloying in molten Sn at 300 °C, followed by sequential chemical and electrochemical dealloying in 0.1 M HCl. During surface alloying, Ni₃Sn₄ intermetallic phases grow via grain boundary diffusion and grooving, forming a dense interlayer at the Ni/Sn interface. After 4 h chemical dealloying, well-aligned and pillar-shaped Ni₃Sn₄ nanoarrays with an average diameter of ∼237 nm remain anchored on the unreacted Ni cores. Prolonged dealloying leads to the dissolution and collapse of these nanoarrays. The formation mechanism is attributed to the selective dissolution of micro-coupling of embedded Sn within the Sn-alloyed shells and Ni₃Sn₄ phases. Subsequent electrochemical dealloying, as nanoporous modification of Ni₃Sn₄ intermetallics nanoarrays, induces Sn leaching, producing Ni-rich nanoporous layers and resulting in 4-fold increase in the surface area. The final catalyst exhibited an overpotential of 244 mV at 10 mA cm⁻² and a Tafel slope of 86.2 mV dec⁻¹, with minimal degradation (69 mV negative shift, <30 mV dec⁻¹ decay) after 5000 LSV cycles. Compared to pure Ni and other NiSn-based catalysts, the Ni-rich porous Ni₃Sn₄ intermetallics nanoarrays exhibit superior HER Kinetics and long-term electrochemical stability. This stepwise surface roughening approach offers an effective route to enhance catalytic performance of metallic wires and porous metals.