Muhammad Usman, Faiqa Nadeem, Hina Ramzan, Nadeem Tahir
The shift toward carbon-neutral energy systems has heightened the focus on sustainable hydrogen production from renewable resources, especially lignocellulosic biomass (LCB). This review comprehensively assesses the role of nanotechnology in photo-fermentative biohydrogen production, framed within an integrated biorefinery context. It highlights advancements in catalysis, underlying mechanisms, and the potential for commercialization. The inherent recalcitrance of lignocellulosic biomass, driven by the interplay of cellulose, hemicellulose, and lignin, necessitates effective pretreatment and hydrolysis to optimize the release of fermentable sugars. A specific emphasis is placed on the role of purple non-sulfur bacteria (PNSB) in photofermentation, highlighting how nitrogenase-mediated hydrogen production is augmented by nanophotocatalysts that enhance electron-transfer efficiency, enzyme activity, substrate conversion, and redox balance. Recent advances in nanomaterials, such as metal oxides, magnetic nanoparticles (MNPs), carbon-based nanostructures, and heterojunction photocatalysts, are examined in detail for their contributions to biomass depolymerization, metabolic regulation, and the optimization of light-harvesting processes. This review goes beyond mechanistic insights by incorporating assessments of Technology Readiness Level (TRL), techno-economic analysis (TEA), and life cycle assessment (LCA) to thoroughly evaluate scalability, environmental impact, and economic feasibility. A SWOT framework provides a clearer understanding of strengths, limitations, and barriers to commercialization, including catalyst deactivation, nanoparticle (NP) toxicity, constraints in reactor design, and the high costs associated with scale-up. While catalytic photo-fermentation remains in the early stages of development (TRL 1-3 for raw biomass systems), targeted advances in catalyst design, improvements in reactor efficiency, and the incorporation of circular bioeconomy principles could significantly enhance its potential for industrial application. This review outlines a detailed framework for enhancing nano-enabled photobiological hydrogen production to achieve sustainability, scalability, and economic competitiveness in biorefinery applications.