Scaling Up Electrodes for Photoelectrochemical Water Splitting: Fabrication Process and Performance of 40 cm2 LaTiO2 N Photoanodes

Abstract

A scalable process for fabrication of particle-based photoanodes is developed. The electrodes are versatilely made of photocatalytically active semiconductor particles, in this case LaTiO₂ N, and optionally coated with cocatalysts and protecting components, all immobilized on a conducting substrate. The involved fabrication steps are restricted to scalable processes such as electrophoretic deposition, annealing in air, and dip coating. Special care is taken to ensure efficient charge transport in-between particles and to the substrate by incorporating conducting connectors. By adapting the fabrication steps, the electrode geometrical dimension is increased from the size of a typical lab electrode of 1 to 40 cm² . The quality of the scale-up process is characterized by comparing the photoanodes in terms of thickness, light-absorption properties, and morphology. For several compositions, the electrochemical performance of both electrode sizes is assessed by measuring the photocurrents and faradaic efficiencies. The comparison revealed a complex upscaling behavior and showed that the photoelectrode size affects performance already on the 0.1 m scale.

Keywords: LaTiO2N; electrode area; energy conversion; photocurrent; water splitting.

Figure 1

SEM images of a) LTON and b) LTONCNT‐composite particles. The scale bar is set to 2 μm.

Figure 2

Lab‐size process versus scale‐up process flow. The difference between lab‐size process and scale‐up process is restricted to step 3, the annealing condition. The labelling of the electrodes indicates the fabrication route: annealing condition N means lab‐size process, annealing condition O means scaled‐up process.

Figure 3

Film thickness of photoanodes fabricated by the scale‐up process measured using profilometry. The black columns indicate the average thickness of 40 cm² electrodes versus the 1 cm² electrodes in blue columns. The thickness profiles are displayed in Figure S7.

Figure 4

UV/Vis transmission spectra of LTONCNT‐photoanodes fabricated by the scale‐up process. LTON spectra are indicated by black (40 cm² electrodes) and grey lines (1 cm² electrodes), whereas LTONCNT spectra are represented by blue (40 cm² electrodes) and cyan lines (1 cm² electrodes). Broken lines label electrodes with cocatalyst coatings.

Figure 5

J–V curves of LTON and LTONCNT electrodes in back illumination a) without and b) with cocatalysts. Dark currents were added as dotted lines.

Figure 6

a) Chronoamperometric measurement and b) oxygen and hydrogen evolution of LTONCNT‐40‐O‐cat. The charges n(e⁻/2) and n(e⁻/4) were obtained by integrating the current I over time and dividing it by 2 and 4, respectively.