Cu-Based Nanosheet Arrays for Water-Splitting

Cu-based electrocatalysts for overall water splitting are less reported. Room-temperature synthesis of cost-effective Cu electrodes to replace precious catalysts remains a great challenge. Herein, CuO with Ni modulation (Ni-CuO) nanosheet arrays were obtained at room-temperature via a feasible two-step strategy, with the chloride counterpart as the precatalyst. HCl plays a key role in the preparation, which facilitates Cu precipitation and corrodes the nickel foam surface to supply a Ni element. Theoretical simulations reveal that Ni modulation can activate the CuO substrate, with Cu rather than Ni as the active site, ascribed to the induced, more delocalized electrons, higher carrier concentration, and increased d-band center. In the alkaline electrolyte, Ni-CuO exhibits a low overpotential of 367 mV to achieve a current density of 200 mA cm–2 toward oxygen generation. Moreover, subsequent room-temperature sulfurization leads to the formation of Ni-CuO-S, which requires a 54 mV overpotential to reach 10 mA cm–2 for hydrogen production. Benefiting from the nanosheet array structure, these two room-temperature obtained electrodes are assembled into an all Cu-based water splitting electrolyzer, which exhibited 10 mA cm–2 at a voltage of 1.55 V with a Faraday efficiency of ∼100%, and a sustainable stability of more than 30 h, suggesting Cu-based electrodes via the room-temperature preparation strategy have the potential for energy conversion and storage applications.