Scalability and Investigation of the Geometrical Features and Shapes of a Tandem Photo-Electrolysis Cell Based on Non-Critical Raw Materials

Tandem photoelectrochemical cells (PECs) are devices useful for water splitting (WS) with the production of oxygen at the photoanode (PE) and hydrogen at the photocathode (PC) by adsorbing more than 75% of the solar irradiation; a portion of the UV/Vis direct solar irradiation is captured by the PA and a diffused or transmitted IR/Vis portion by the PC. Herein, Ti-doped hematite (PA) and CuO (PC) were employed as abundant and non-critical raw semiconductors characterised by proper band gap and band edge banding for the photoelectrochemical WS and absorption of sunlight. The investigation of inexpensive PEC was focused on the scalability of an active area from 0.25 cm2 to 40 cm2 with a rectangular or square shape. For the first time, this study introduces the novel concept of a glass electrode membrane assembly (GEMA), which was developed with an ionomeric glue to improve the interfacial contact between the membrane and photoelectrodes. On a large scale, the electron–hole recombination and the non-optimal photoelectrodes/electrolyte interface were optimized by inserting a glass support at the photocathode and drilled fluorine tin oxide (FTO) at the photoanode to ensure the flow of reagents and products. Rectangular 40 cm2 PEC showed a larger maximum enthalpy efficiency of 0.6% compared to the square PEC, which had a value of 0.37% at a low bias-assisted voltage (−0.6 V). Furthermore, throughput efficiency reached a maximum value of 1.2% and 0.8%, demonstrating either an important effect of the PEC geometries or a non-significant variation of the photocurrent within the scalability.