Strain-induced Ni–Re alloy electrodeposits as efficient electrocatalysts for water-splitting reactions

A novel Ni-Re alloy with varying Ni and Re compositions was fabricated as a highly efficient, non-precious metal catalyst for water splitting in alkaline media. The alloy was synthesized <i>via</i> a facile one-step electrodeposition method. The prepared Ni-Re alloy demonstrated excellent electrocatalytic activity towards both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Notably, upon electrochemical activation, which induces lattice strain, the overpotential of the HER significantly decreased from 103 mV to 65 mV and that of the OER decreased from 330 mV to 320 mV. The corresponding Tafel slopes were 33 mV dec^-1 for the HER and 66 mV dec^-1 for the OER. When evaluated for overall water splitting, the initial cell voltage was 1.74 V, which decreased to 1.65 V after 24 hours of stability testing at 10 mA cm^-2. XRD and HR-TEM analyses confirmed the introduction of lattice strain in the range of 1.5-6.8% through electrochemical activation. The alloy with the highest lattice strain (6.8%) exhibited the best electrocatalytic performance, suggesting a strong correlation between the lattice strain and the catalytic activity.