Optimization of z-scheme Bi_0.5Na_0.5TiO₃/RGO-Co₃O₄ composite catalyst for water splitting reaction through piezo-photocatalysis

Utilizing strain-induced polarization to amplify the performance of photo-catalytic water-splitting systems has garnered significant attention in view of clean H₂ evolution with no environmental footprint. However, achieving efficient charge separation, high underwater suspension efficiency, and sustained cyclic stability remains a persistent challenge. In this study, we employed a classic low-temperature ball milling technique to synthesize rhombohedral bismuth sodium titanate phase B_0.5Na_0.5TiO₃ as a matrix material. One-step superimposed reduced graphene oxide with cobalt oxide loading RGO-Co₃O₄ is used as reinforcement. The cobalt oxide (Co₃O₄) is expected to speed up classically slow OER reaction. The addition of reinforcement lowers the band gap of our material and makes it more visible light active to optimize full spectrum absorption. We report a 14.79% increase in H₂ evolution with the addition of reinforcement and optimal H₂ evolution was achieved with 5% RGO-Co₃O₄ (517 μmol/g-h). After the introduction of simultaneous photo and piezoelectric potential by using an ultrasonicator, H₂ evolution is much enhanced 109 μmol/g-h surpassing piezo catalysis 66 μmol/g-h and photo catalysis 64 μmol/g-h. Herein, we also explore renewable alternatives using manure and seawater revealing improved H₂ evolution that is 1.8% and 50.4% respectively. Additionally, the piezo-photo catalyst demonstrates remarkable performance without a sacrificial agent further highlighting its exceptional potential. Moreover, we also uncover the role of Co₃O₄ as a co-catalyst and RGO as a promoter in direct and indirect z-schemes for water splitting. This work provides insight into harnessing and designing ingenious composites for efficient and stable piezo-photo catalysts for efficient and stable water-splitting systems.