Structural transformation between rutile and spinel crystal lattices in Ru-Co binary oxide nanotubes: enhanced electron transfer kinetics for the oxygen evolution reaction

A variety of binary Ru-Co mixed oxide nanotubes (Ru x Co 1− x O y with x = 0.19, 0.33, 0.47, 0.64 and 0.77) were readily synthesized via electrospinning and subsequent calcination. Ru x Co 1− x O y nanotubes (0 < x < 0.77) were composed of both rutile (Ru in RuO 2 is replaced with Co) and spinel (Co in Co 3 O 4 is replaced with Ru) structures. This elemental substitution created oxygen vacancies in the rutile structure and also resulted in the incorporation of Ru 3+ in the octahedral sites of the spinel structure. The as-prepared Ru x Co 1− x O y nanotubes were investigated for oxygen evolution reaction (OER) electrocatalytic activity in 1.0 M HClO 4 aqueous solution. Ru x Co 1− x O y nanotubes with x ≥ 0.47 presented an excellent OER activity comparable to pure RuO 2 , known to be the best OER catalyst. Even after more than half of the noble/active Ru content was replaced with cheap/less-active Co, Ru 0.47 Co 0.53 O y showed a good OER activity and a greatly improved stability compared to RuO 2 under the continuous OER. These attractive catalytic properties of Ru x Co 1− x O y can be attributed to the relatively large surface area of the tubular morphology and the substituted structures, presenting feasibility as a practical and economical OER catalyst. A variety of binary Ru x Co 1− x O y ( x = 0.19, 0.33, 0.47, 0.64 and 0.77) were synthesized via electrospinning and subsequent calcination, and investigated for OER electrocatalytic activity in 1.0 M HClO 4 aqueous solution.