Flexible electrodes, particularly paper electrodes modified with polypyrrole, have shown promise in energy-related applications. We have earlier demonstrated the usage of paper electrodes modified with polypyrrole as a flexible and suitable photoanode for photoelectrochemical water splitting (PEC). Further, modification of this electrode system with an appropriate tandem absorber system for solar fuel production is interesting in developing efficient photoanodes. In this study, we study the PEC performance of flexible polypyrrole-based paper photoanodes (PPy-PAs) by decorating them with rGO@Cu2Zn- SnS4 chalcopyrites (rGO@CZTS/PPy-PAs). The lower bandgap (~ 1.5 eV) of the rGO@CZTS/PPy-PAs system allows for efficient visible light absorption, substantially improving PEC water-splitting reactions. The rGO@CZTS/PPy-PAs exhibited an enhanced current density of ~ 13.2 mA/cm2 at 1.23 V vs RHE, ABPE of ~ 1.5%, and a hydrogen evolution rate of 177 μmoles/min/cm2. Overall, rGO@CZTS/PPy-PAs showed 2.1-fold, 1.1-fold, and 1.4-fold enhancement in photocurrent activity over PPy-PAs, CZTS/PPy-PAs, and rGO/PPy-PAs, respectively. The usability of rGO@CZTS/PPy-PAs is established in the form of stable photocurrent for more than 200 min. These findings open new possibilities for developing modified PPy PAs as flexible PEs for efficient solar-driven PEC devices and give directions on improving flexible PEs for flexible and efficient solar-driven PEC systems.

rGO@Cu2ZnSnS4 chalcopyrites modified polypyrrole paper-based photoanode for solar water splitting
    Abstract
        Graphical abstract
    1 Introduction
    2 Methods
        2.1 Preparation of PPy-based flexible paper photoanode substrates
        2.2 Hybrid design of rGO@CZTSPPy-PAs
        2.3 Photoelectrochemical water splitting studies
        2.4 Characterization
    3 Results
        3.1 Material characterization
        3.2 Photoelectrode characterization and PEC water splitting
    4 Conclusions
    Acknowledgements 
    References

• Anupma Thakur(Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India, Materials Science and Sensor Application, CSIR-Central Scientific Instruments Organisation, Sector‑30C, Chandigarh 160030, India) Corresponding author
• Pooja Devi(Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India, Materials Science and Sensor Application, CSIR-Central Scientific Instruments Organisation, Sector‑30C, Chandigarh 160030, India)