Rational design of CoNi alloy and atomic Co/Ni composite as an efficient electrocatalyst

Highly efficient, non-precious and stable electrocatalysts for both oxygen (O2) reduction reaction (ORR) and oxygen evolution reaction (OER) have drawn attention as alternatives to noble-metal catalysts. The rational construction of dual-functional catalysts is meaningful because most nanomaterials can perform only a single electrocatalytic activity. Herein, nitrogen (N)-doped carbon (C) nanotubes encapsulating CoNi alloy (CoNi@NCNTs) nanoparticles coupled with a cobalt (Co) and nickel (Ni) dual atom hybrid are successfully designed and synthesized through a simple metal–organic-framework-assisted strategy, which are explored as a catalyst for ORR and OER. The optimized catalyst exhibits highly efficient bifunctional catalytic activity with a low voltage spacing of 0.78 V between an overpotential of 370 mV (at 10 mA/cm2) toward OER and a half-wave potential of 0.822 V toward ORR, as well as high durability. The excellent electrocatalytic performance should be attributed to the advantages of uniformly dispersed CoNi alloy nanoparticles, highly conductive nitrogen-doped carbon nanotubes and the formation of metal–Nxspecies. This work provides a novel strategy for rationally designing bifunctional catalysts for reversible energy conversion.