MOFs-derived Zn-doped ceria/rGO nanocomposites as photoanode for solar-driven water splitting

Abstract

The present investigation focuses on the designing of photoanodes for photoelectrochemical (PEC) water splitting. For this, metal–organic framework (MOF)-derived Zn-doped ceria (CeO₂) nanobars (NBs) are modified herein using reduced graphene oxide (rGO). The bare CeO₂ NBs and Zn–CeO₂ nanocomposites (NCs) are synthesized through calcination of the respective MOFs, while a simple sonochemical treatment is used to create ternary Zn–CeO₂/rGO (ZCR-3) NCs with 1 wt% rGO content. The primary goal of integrating rGO and Zn²⁺ ion doping is to enhance the PEC performance of CeO₂ NBs by increasing conductivity, and stability, and facilitating well-organized charge transfer, owing to synergistic effects between the components. The high surface area with increased oxygen vacancies within ZCR-3 NCs is studied using N₂ adsorption–desorption isotherms and electron spin resonance (ESR) analysis. This is further perceived by PEC testing of the synthesized samples, revealing the highest current density of 2.228 mA cm⁻² at 1.23 V vs. reversible hydrogen electrode (RHE) for the ternary ZCR-3 NC-based photoanode, which is almost 2 and 6 times greater than that of Zn–CeO₂ NCs and bare CeO₂ NB-based photoanodes, respectively. Additionally, the stability of the photoanodes is evaluated under prolonged water splitting conditions and modeled using a machine learning-based recurrent neural network (RNN) with a long short-term memory (LSTM) algorithm. The results of this study suggest that rGO integration with MOF-derived CeO₂ nanostructures holds significant potential for developing efficient and stable photoanodes for water splitting applications.