Chiral helically grooved gold nanoarrows for concurrently enhancing oxygen and hydrogen evolution from electrochemical water splitting

Abstract

Electrocatalytic water splitting shows a tremendous promise for storing green and intermittent electricity into storable fuels, paving a sustainable way toward carbon neutrality. The exploration of a bifunctional electrocatalyst for simultaneously enhancing oxygen evolution reaction and hydrogen evolution reaction is at the core yet remains a grand challenge, especially operated in the same electrolyte. In this work, mesoscale gold nanoarrows with special chiral morphology are synthesized for electrocatalytic water splitting. In the same electrolyte of 1 M KOH aqueous solution, the as-designed chiral R-/L-helically grooved gold nanoarrows (R-/L-heliGNAs) demonstrated significantly enhanced performance in both hydrogen evolution reaction and oxygen evolution reaction with overpotentials of 186 and 355 mV at 10 mA cm⁻², respectively, compared to the achiral counterpart. For oxygen evolution reaction, the performance is even comparable to commercial notable metal catalysts, i.e., RuO₂, of which the overpotential is 310 mV under the same measured conditions. The spin-polarized conductive atomic force microscope (c-AFM), finite-difference time-domain simulation, in combination with electrochemical investigations, show that the chirality of R-/L-heliGNAs makes a substantial contribution toward the remarkable performance by enhanced electric field distribution for hydrogen evolution reaction and by tuning the spin states of the electrons for oxygen evolution reaction. This study presents an encouraging strategy for simultaneously promoting hydrogen evolution reaction and oxygen evolution reaction that operated in the same electrolyte by imparting chirality toward a mesoscale inorganic electrocatalyst, showing a grand promise for opening up a new way for electrocatalytic water splitting toward green hydrogen.