Chirality-enhanced oxygen and hydrogen production by water splitting over a hydrogen-bonded organoelectrocatalyst

Abstract

Electrocatalytic water splitting has emerged as the most promising source of renewable hydrogen to support energy conversion/storage and chemical manufacturing as a part of the global circular economy. However, overall water splitting to produce green H2 through the hydrogen evolution reaction (HER) is limited by the high overpotential and sluggish kinetics of the associated oxygen evolution reaction (OER). Control over electron spin at the electrode-electrolyte interface may lower the thermodynamic barriers, and hence improve the catalytic efficiency, of both reactions. We employ compositionally identical chiral and racemic hydrogen-bonded organocatalysts, comprised of (ionised) melamine and L-, D-, or DL-tartaric acid, to demonstrate chirality-enhanced organoelectrocatalysis. Chiral electrocatalysts promote both OER and HER compared to their racemic counterpart, as evidenced by lower overpotential (384 (L)/379 (D) mV vs 483 mV (DL) for OER, and 143 mV (L)/144 mV (D) vs 358 mV (DL) for HER), a change in the rate-determining step, and an approximately four-fold increase in current density. This work highlights the impact of catalyst chirality on enhancing electrocatalytic water splitting to hydrogen and oxygen, and the promising performance of inexpensive and environmentally benign organoelectrocatalysts.