Nickel-Based Hybrid Material for Electrochemical Oxygen Redox Reactions in an Alkaline Medium

Abstract

Synthesizing active and stable oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts in a cost effective way remains a challenge in the fuel cells and rechargeable metal–air batteries community. Here, we report a nickel-based hybrid material, namely [Ni3(BPE)4(BTB)2(H2O)2]·2DMF·2H2O [where BTB = 1,3,5-tris(4-carboxyphenyl)benzene and BPE = 1,2-bis(4-pyridyl) ethane] and Ni-BTB-BPE for ORR and OER. Structural analysis of Ni-BTB-BPE showed that the BTB ligand connectivity with a nickel center formed an interesting two-dimensional Kagóme-type lattice and BPE ligand connectivity with the layers to form the three-dimensional structure. With the aid of the Ni (E(Ni2+/3+)) redox site, the electrochemical surface concentration of Ni2+/3+ was calculated to be 5.49 nM/cm2. Ni-BTB-BPE/C exhibited 108.95 A gNi –1 of ORR mass activity at 0.75 V versus RHE. The catalyst showed a completely methanol tolerant ORR performance. The four-electron turn-over frequency (2.24 electrons [Ni]−1 s–1 at 0.70 V vs RHE) of Ni-BTB-BPE/C was found to be 2.67 times higher than that of the two-electron one, which indicates the higher selectivity of Ni-BTB-BPE/C catalyst in the four-electron pathway (OH– as a predominant product). Ni-BTB-BPE/C has performed ORR/OER activity with a bi-functionality index value of 0.9 at 1 mA cm–2.