Hydrogen evolution reaction activities of electrodeposited nanocrystalline Ni–Mo thin films in alkaline baths

The hydrogen evolution reaction (HER) electrocatalytic activities normalized to electrochemically active surface area (ECSA) were systematically evaluated and correlated with its composition (i.e., Mo content up to 26 at. %), crystal structure (i.e., face-centered cubic (fcc) to orthorhombic phase and the mixed phases with different phase ratios), and crystallinity. The electrodeposited with mixed phases exhibited highest ECSA (up to 228 cm2 per 1 cm2 geometric surface area) compared to deposits with single phase, which serves as the dominant factor to enhance exchange current density and overpotential. Low overpotentials per ECSA were observed with Mo content of 5.16 at% (fcc) and 24.1 at% (mixed phases). After normalizing with ESCA, The Tafel slope and exchange current density were indifference with Mo content, crystal phase, and grain size. The metallic Ni–Mo thin films have low mixed potential and overpotential at 10 mA/cm2 of 20 mV and 120 mV, respectively.