Role of active area on photoelectrochemical water-splitting performance of inverse opal CuBi2O4 photocathodes

Copper bismuth oxide (CuBi2O4), a ternary metal oxide is considered as one of the best photocathodes for photoelectrochemical water splitting. However, to date, the majority of research activities have been aimed at developing photocathodes at laboratory scale (<= 1 cm(2) electrochemical active area) and the issues that arise with scaling up have scarcely been addressed. Herein, we demonstrate a layered self-assembly method for fabricating uniform and different electrochemical active area (1-15 cm(2)) inverse opal structured CuBi2O4 photocathodes, intending to validate it for photoelectrochemical hydrogen evolution under solar irradiation. After scaling up, it was found that CuBi2O4 with an active area of 5 cm(2) exhibits the best photocurrent density (3.24 mA/cm(2) at 0.6 V vs. RHE) and Faradaic efficiency (98.06 %). The scaling-up strategy and low-cost method employed for the fabrication of photocathodes could be expanded to large-scale applications associated with the manufacturing of highly efficient photoelectrochemical hydrogen production devices.