The key to realizing highly efficient hydrogen production by water electrolysis is to elevate the electrocatalytic activity of the oxygen evolution reaction (OER) as a ratedetermining step. Herein, we demonstrate that the electrochemical activation process of the CoP nanoflower supported on carbon cloth (CoP/CC) can remarkably reduce the OER overpotential by about 123 mV, which only requires an ultralow overpotential of 176 mV at the current density of 10 mA cm −2 . Correspondingly, the voltage of the assembled CoP/CC||CoP/CC electrolyzer is also greatly decreased from 1.64 to 1.49 V at 10 mA cm −2 . We further find that during the OER process, at least a three-step electrooxidation process occurs on the catalyst surface in different potential ranges: under lower potentials, the ultrathin CoP nanosheets are oxidized to divalent CoO, then further oxidized to trivalent β-CoOOH under moderate potentials, and even transformed to Co IV species under high potentials. Such produced oxidized species are favorable to the formation of OOH* active intermediates or directly serve as OOH* active intermediates of the rate-determining step, thus facilitating the OER process. Meanwhile, the generation of porous surfaces, downsizing particles, active intermediate crystal structures, and new interfaces during the OER activation process can also lower the energy barrier, further accelerating the OER process.
Transition
metal borides Co–B and Co–Ni–B
are prepared by a simple chemical reduction method and used to construct
a new all-boride aqueous solution battery with borides used for both
the anode and cathode. This all-boride-based battery exhibits an excellent
electrochemical property and extreme frost tolerance. The results
of the electrochemical performance test demonstrate that the specific
capacity of this all-boride battery reaches 332.4 mA h g–1 at a current density of 500 mA g–1 and is maintained
at 280 mAh g–1 with a high discharge current density
of 8 A g–1 as a result of the rapid electrochemical
reaction kinetics and high electronic conductivity. This all-boride
battery can continue to work at low temperatures (−40 °C)
and exhibits good electrochemical performance; therefore, it can be
used under extreme cold weather conditions. The electrode material
of the all-boride battery is simple to prepare, is energy-saving,
does not require special equipment or a special environment during
assembly, and thus shows promise as a new energy storage device.
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