Activity Enhancement of Layered Cobalt Hydroxide Nanocones by Interlayer Spacing Tuning and Phosphidation for Electrocatalytic Water Oxidation in Neutral Solution
Due to the low cost, abundant reserves and redox features, electrocatalysts based on 3d transition metals have been greatly evaluated and considered as the promising candidates to currently commercial noble metal-based materials. Designing elaborate structures and favorable phase composition is regarded effective to activity improvement in electrocatalysis. Herein, three kinds of layered cobalt hydroxide nanocones (NCs) with tunable interlayer spacing determined by the intercalated anion species were prepared. Because of the larger interlayer spacing which might be beneficial for the faster mass transfer, dodecyl sulfate (DS−) ions-intercalated layered cobalt hydroxide NCs yielded a current density of 5 and 10.65 mA cm−2 at an overpotential of 0.50 and 0.57 V in electrolytic oxygen evolution reation (OER) under neutral phosphate buffer solution (PBS), respectively, overpassing the counterparts with decreased layer distances determined by intercalated acetate (CH3COO−) or nitrate (NO3−) anions. When a further phosphidation treatment was adopted on NO3−-intercalated cobalt hydroxide NCs, cobalt phosphide (CoP) product with the conical morphology well maintained was obtained, which reduced the overpotential of ~20 mV to reach the anodic exchange current density of 5 mA cm−2. The activity enhancement induced by interlayer spacing tuning and phosphidation offers a great promise for developing high-activity catalysts by delicately designing phase structure and composition for electrochemical energy conversion.