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 electrocatalyst. A large applied 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 similar to 45% saving in energy to achieve an electrochemical hydrogen generation rate of 3x10(16) molecules cm(-2) s(-1) (current density 10 mA/cm(2)) 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 eta(10) 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 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/cm(2). 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.

Automated summary

The electrochemical generation of fuels through electrochemical oxidation/reduction of radicals is a green approach, but suffers from slow kinetics. In this study, a saving of about 45% in energy was achieved for the electrochemical hydrogen generation rate by enhancing the reagent concentration through localized electric field. Using laser-induced periodic surface structured (LIPSS) electrodes, the overpotentials for HER and OER were decreased, and the energy reduction capability was demonstrated in various electrolytes. The LIPSS-patterned electrodes also showed enhanced stability and lower potential requirements for driving current density.