Contributions to activity enhancement via Fe incorporation in Ni-(oxy)hydroxide/borate catalysts for near-neutral pH oxygen evolution

Abstract

Ni–borate materials are oxygen evolution catalysts that operate at near-neutral pH and have been found previously to improve due to structural changes induced via anodic conditioning. We find that this increased activity after conditioning at 0.856 V vs. SCE, as measured on a turn-over frequency basis (TOF) at 400 mV overpotential (TOF = 0.38 s⁻¹), accompanies significant Fe incorporation (14%). Films conditioned in Fe-free electrolyte exhibit ∼10 times lower activity (TOF = 0.03 s⁻¹). By co-depositing Fe–Ni we demonstrate high activity without conditioning (TOF = 0.24 s⁻¹) which improves further with shortened (∼30 min) conditioning (TOF = 1.4 s⁻¹).