Interleaved biphasic p–n blended copper indium selenide photoelectrode and its application in pulse-driven photoelectrochemical water splitting

Conventional photoelectrodes have shown dominantly single-signal photoelectrochemical (PEC) performance under reverse-bias, where only photo-generated minority carriers are involved in water splitting reactions. The extraordinary dynamic-mode operation of PEC water splitting is suggested herein, using the heterophasic copper indium selenide (CIS) with coexisting p- and n-type phases. CIS photoelectrodes with an interleaved p-n blended structure generate substantial photocathodic/-anodic currents resulting in transient spikes followed by saturation at negative/positive potential under light illumination. Then, the interleaved inner-depletions function as the charge transport pathway. Pulsed-bias (0 and 0.8 V vs. reversible hydrogen electrode) with a suitable frequency applied to the p-n blended CIS photoelectrodes under steady light illumination results in an extremely high photocurrent density of approximately 25 mA/cm² (spike) and 10 mA/cm² (saturation). Furthermore, the pulse-driven PEC operation shows remarkably high hydrogen evolution efficiency by suppressing the formation of large-size cluster bubbles and an intrinsic electric double layer.