Oxalate-based Ni–Fe MOF/CNT composites for highly efficient oxygen evolution reaction

Abstract

Nickel-iron non-precious catalysts for oxygen evolution reaction (OER) have attracted much attention in recent years due to their low-cost and excellent catalytic performance. In this work, a green synthesis method of adding carbon nanotubes (CNTs) into oxalate-based Ni–Fe metal organic framework (Ni–Fe MOF) obtained a highly efficient OER catalyst, Ni–Fe MOF/CNT. By tuning the amount of CNTs added, it was found that 30% (mass fraction) addition of CNTs showed the best OER performance, with an over-potential of only 240 mV at the current density of 10 mA cm−2 and a small Tafel slope of 37.2 mV dec−1 in 1 M KOH solution. Further study showed that the addition of CNTs did not obviously change the Ni–Fe MOF phase. The excellent catalytic activity should be attributed to the formed Ni–Fe hydroxides during the OER reaction in alkaline solution. The result revealed that CNTs can effectively improve the conductivity of oxalate-based Ni–Fe MOF, and further enhance the OER catalytic activity. This work provides good references for the synthesis of highly efficient non-precious OER catalysts using simple green methods.