Laser-induced periodic surface structured electrodes with 45% energy saving in electrochemical fuel generation through field localization

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 elec-trocatalyst. A large applied electrode potential can enhance the fuel generation efficiency via enhancing the radical con-centration around the electrocatalyst sites, but this comes at the cost of electricity. Here, we report about a ～45％ saving in energy to achieve an electrochemical hydrogen generation rate of 3×1016 molecules cm–2s–1 (current density: 10 mA/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 η10 overpotentials for HER and OER are decreased by 40.4 and 25％, 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 sea-water. Importantly, when two LIPSS patterned electrodes were assembled as the anode and cathode into a cell, it re-quires 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.