Photoelectrochemical oxidation performance via a protective, catalytic self-limiting Ni-Co alloys by electrodeposition

Abstract

Scalable energy conversion/storage by water splitting is significantly hindered by the slow kinetics of oxygen evolution reaction (OER). The development of electrochemical catalysts with low cost and high turn-over efficiency, or the usage of a photoanode in a photoelectrochemical (PEC) cell using a semiconductor with a proper protective layer are among the possible solutions. Herein, a binary alloy film of Ni-Co grown under self-limiting electrodeposition conditions is investigated and continuous ultrathin films with various compositions are generated. The self-limiting deposition mechanism is validated by potential transients and XPS depth profiles; both methods support a film thickness independent of electrodeposition time when the self-limiting deposition condition is attained with a deposition time no more than 1s. The Ni-Co alloy film exhibits a reduced potential of 217 mV at 10 mA cm−2 for electrochemical water oxidation kinetics compared to pure Ni in 1M KOH solution, with an optimum Ni2+/ (Ni2++Co2+) fraction of 0.75. The Ni-Co film deposited on GaAs is further investigated for photoelectrochemical oxidation in a ferri/ferrocyanide solution while the stability towards photocorrosion under light in an aqueous solution containing K3Fe(CN)6/K4Fe(CN)6 is significantly enhanced, resulting in a photocurrent retention improvement from 82.4 to 91.8% in the first 300s.