Scalable and durable photoelectrodes are essential for technological breakthroughs in photoelectrochemical systems, yet the fragility of nanostructured photocatalyst materials in industrially relevant operating conditions is rarely explored. Herein, we advance understanding of the importance of morphology and temperature on stability and performance of nanostructured WO3|BiVO4|NiFeOOH photoanodes. The integration of a planar WO3 seed layer beneath nanostructured WO3, improved mechanical stability at 40°C with flowing electrolyte approximately twofold compared with materials where a seed layer was not integrated. This work provides a pathway through which robust photoelectrode systems can be engineered to enable the advancement of up-scaled photoelectrochemical water splitting.