  Electrochemical oxidation-reduction of radicals is a green and
environmentally friendly approach to generating fuels. These reactions,
however, suffer from sluggish kinetics due to a low local concentration of
radicals around the electrocatalyst. A large electrode potential can enhance
the fuel generation efficiency via enhancing the radical concentration around
the electrocatalyst sites, but this comes at the cost of electricity. Here, we
report about a 45 percent saving in energy to achieve an electrochemical
hydrogen generation rate of 10 mA per cm2 through localized electric
field-induced enhancement in the reagent concentration (LEFIRC) at
laser-induced periodic surface structured (LIPSS) electrodes. The finite
element model is used to simulate the spatial distribution of the electric
field to understand the effects of LIPSS geometric parameters in field
localization. When the LIPSS patterned electrodes are used as substrates to
support Pt-C and RuO2 electrocatalysts, the overpotentials for HER and OER are
decreased by 40 and 25 percent, respectively. Moreover, the capability of the
LIPSS-patterned electrodes to operate at significantly reduced energy is also
demonstrated in a range of electrolytes including alkaline, acidic, neutral,
and seawater. Importantly, when two LIPSS patterned electrodes were assembled
as the anode and cathode into a cell, it requires 330 mVs of lower electric
potential with enhanced stability over a similar cell made of pristine
electrodes to drive a current density of 10 mA/cm2. This work demonstrates a
physical and versatile approach of electrode surface patterning to boost
electrocatalytic fuel generation performance and can be applied to any metal
and semiconductor catalysts for a range of electrochemical reactions.
