Hydrogen production through visible light-induced water splitting using carbon-based CoCe-MOF as novel photocatalyst

Abstract

Hydrogen as a green energy source has been increasingly emerging to decarbonize electricity production and transportation fuels, serving as a proper replacement for current fossil fuel sources. Thus, massive endeavors are done lately to develop sustainable processes for hydrogen generation. Among those methods, hydrogen production through photocatalytic aqueous reforming of methanol coupled with water splitting is considered one of the most efficient sustainable routes. In line with this methodology, the current research study introduces two novel photocatalysts (CoCe-MOF and its composite with reduced graphene oxide) for hydrogen generation from a water-methanol mixture. The textural, morphological, optical, and structural characteristics of the prepared materials were verified through various analytical techniques. Both structures revealed reasonable hydrogen productivity; however, the composite-MOF showed increased reactivity. The composition of the produced gases upon using both structures varied significantly. The explicit differences in the activities of both photocatalysts are attributed to the presence of graphene species in the composite-MOF. Statistical modeling was employed to comprehensively design the hydrogen production experiments based on preliminary experimental results that were obtained under different operating variables. A maximum hydrogen productivity of 560 mmol h⁻¹ g⁻¹, along with a hydrogen percentage of 60 % in the produced gas, was detected for the composite-MOF under a reaction time of 1.5 h, 4 g/L as a photocatalyst dose, and a radiation power equals 3 W cm². Both the model predictions and practical investigations were in agreement, showing that the photocatalyst dose and operating time are the most influential parameters in the hydrogen generation process. Furthermore, the recyclability of the composite photocatalyst was evaluated over six consecutive cycles under optimized conditions, confirming its increased stability. This excellent stability demonstrates the potential of the composite-MOF for long-term hydrogen production applications, reflecting the feasibility of its usage as efficient/reusable photocatalyst.