Superior Electrocatalytic Oxygen Evolution of Nickel-Based Metals Modulated by Controllable Graphene Layers via Interfacial Redox Process

Metallic Ni is widely used for oxygen evolution reaction (OER) catalysis. It acts as a precatalyst and undergoes surface reconstruction into NiOOH, which is the active species used in OER. Consequently, OER performance is highly related to the NiOOH structure, which is determined by the precatalyst. Thus, the modulation of metallic Ni to obtain superior NiOOH is critical. In this paper, an interfacial redox modulation strategy is proposed to oxidize a Ni foam (NF) surface into the desired Ni 2+ species using electrochemically exfoliated graphene (EG). OER-favorable γ-NiOOH on EG-oxidized NF was investigated under anodic potentials by in situ techniques, whereby the formation of inferior β-NiOOH was found to be inhibited. Single Ni atoms and clusters were anchored onto the EG layers after reduction. The altered γ-NiOOH and Ni single atoms and clusters improved the OER performance of the EG-oxidized NF with low overpotential and enhanced stability. Subsequently, controllable EG and Ni-based metals were used to verify the versatility of the proposed interfacial redox modulation strategy. The optimized EG-oxidized NiFe system achieved an overpotential of 243 mV at 10 mA‧cm −2 and long-term stability at 500 mA·cm −2 for 100 h.