Table 1_Decoupling bulk composition and alloying effects in Ni-Mo materials for electrocatalytic hydrogen evolution at near-neutral pH.docx

This includes HER at near-neutral pH conditions relevant to, e.g., microbial electrosynthesis (MES). So far, the role of the Ni:Mo ratio in bulk for determining HER performance remains unclear, especially for commercially available powdery electrocatalysts.

Here, we examined commercial Ni-Mo powders with different nominal Ni:Mo ratios to assess how composition and mass loading influence HER performance. Despite differences in bulk Ni:Mo ratios, no significant variation in HER performance was observed at equal mass loadings. In contrast, increasing the electrocatalyst mass loading from 0.35 ± 0.04 to 1.30 ± 0.07 mg cm⁻² consistently improved HER performance, decreasing the overpotential at −1 mA cm⁻² from 463 ± 50 to 210 ± 9 mV, with an intermediate value of 367 ± 33 mV at a loading of 0.61 ± 0.02 mg cm⁻².