Triggering efficient reconstructions of Co/Fe dual-metal incorporated Ni hydroxide by phosphate additives for...

Alkaline electrochemical water splitting has been considered as an efficient way for the green hydrogen production in industry, where the electrocatalysts play the critical role for the electricity-to-fuel conversion efficiency. Phosphate salts are widely used as additives in the fabrication of electrocatalysts with improved activity, but their roles on the electrocatalytic performance have not been fully understood. Herein, we fabricate Co, Fe dual-metal incorporated Ni hydroxide on Ni foam using NaH₂PO₄ ((Co, Fe)NiO_xH_y-pi) and NaH₂PO₂ ((Co, Fe)NiO_xH_y-hp) as additive, respectively. We find that (Co, Fe)NiO_xH_y-hp with NaH₂PO₂ in the fabrication shows high activity and stability for both HER and OER (a overpotential of -0.629 V and 0.65 V at 400 mA cm^-2 for HER and OER, respectively). Further experiment reveals that the reconstructed structures of electrocatalyst by using NaH₂PO₂ (hp) endow high electrocatalytic performances: (1) in-situ generated active metal improves the accumulation, transportation and activity of hydrogen species in the HER process; and (2) in-situ generated poor-crystalline hydroxide endows superior charge/mass transportation and kinetics improvements in the OER process. Our study may provide an insightful understanding on the catalytic performance of non-precious metal electrocatalysts by controlling additives and guidance for the design and synthesis of novel electrocatalysts.