Modulation of Volmer step for efficient alkaline water splitting implemented by titanium oxide promoting surface reconstruction of cobalt carbonate hydroxide

The sluggish water dissociation (Volmer step) is a rate-limiting step slowing down alkaline hydrogen evolution reaction (HER), and therefore hinders the efficient industrial production of clean hydrogen resource. In this work, we report that the Volmer step can be facilitated by in-situ surface reconstruction on a composite between cobalt carbonate hydroxide and titanium oxide (TiO2@CoCH), and the resultant activated structure turns to be a highly efficient electrocatalyst for alkaline HER. Experimental characterization and density functional theory calculation evidence that under HER potential the smooth TiO2@CoCH surface is roughened and Co interstitial defects in TiO2 are formed, which are energetically favorable for Volmer step. The activated composite exhibits an overpotential of 99 ? 6 mV for a current density of 20 mA cm-2 and 187 ? 21 mV for 100 mA cm-2, suggesting that TiO2@CoCH is one of promising non-precious metal electrocatalysts for HER in alkaline media.