High-Valence-State NiO/Co3O4 Nanoparticles on Nitrogen-Doped Carbon for Oxygen Evolution at Low Overpotential

The electrocatalytic oxygen evolution reaction (OER) plays a critical role in sustainable energy conversion and storage, but OER is severely hampered owing to the lack of highly efficient catalysts. Here, we report an efficient electrocatalyst, with NiO/Co3O4 nanoparticles decorated on nitrogen-doped carbon (NiO/Co3O4@NC). Abundant high-valence Ni3+ and Co3+ species were observed on the surface of the hybrid due to the strong NC–metal oxide and NiO–Co3O4 interactions. This unique structure leads to excellent OER performance, delivering a very low overpotential of 240 mV@10 mA·cm–2 on glassy carbon and 200 mV@10 mA·cm–2 on Ni foam in KOH and having a turnover frequency (@350 mV overpotential) 6 and 16 times higher than that of IrO2 and RuO2, respectively.