Porous Ni1-xCuxO Nanowire Arrays as Noble-Metal-Free High-Performance Catalysts for Ammonia-Borane Electrooxidation

The design and fabrication of efficient inexpensive electrocatalysts are critical for electrochemical energy conversion technologies. Control and understanding of electronic configuration at the active sites are of fundamental importance to achieve this goal. Herein, highly porous Ni1-xCuxO (p-Ni1-xCuxO) nanowire (NW) arrays grown on carbon fiber paper (CFP) were synthesized, characterized, and utilized as high-performance catalytic anode for catalyzing the ammonia-borane (AB) electrooxidation reaction (ABOR). This electrocatalyst shows exceptional electrocatalytic properties including an extremely low onset potential (-0.316 V vs the reversible hydrogen electrode (RHE)), a high Faradaic efficiency (>98%), and long-term durability toward the ABOR, far outperforming the noble metal-based catalysts. Reaction free energies computed as a function of electrode potential by density-functional theory indicate that doping of Cu for Ni1-xCuxO is favorable for energetically decreasing the energy barriers in the multistep reaction pathways. The modulation of the electronic structure of bimetallic Ni1-xCuxO catalysts underlies the catalytic mechanism by the electronic coupling effect between Ni and Cu.