The global imperative for clean energy solutions has positioned photocatalytic water splitting as a promising pathway for sustainable hydrogen production. This review comprehensively analyzes recent advances in TiO₂-based photocatalytic systems, focusing on materials engineering, water source effects, and scale-up strategies. We recognize the advancements in nanoscale architectural design, the engineered heterojunction of catalysts, and cocatalyst integration, which have significantly enhanced photocatalytic efficiency. Particular emphasis is placed on the crucial role of water chemistry in photocatalytic system performance, analyzing how different water sources—from wastewater to seawater—impact hydrogen evolution rates and system stability. Additionally, the review addresses key challenges in scaling up these systems, including the optimization of reactor design, light distribution, and mass transfer. Recent developments in artificial intelligence-driven materials discovery and process optimization are discussed, along with emerging opportunities in bio-hybrid systems and CO₂ reduction coupling. Through critical analysis, we identify the fundamental challenges and propose strategic research directions for advancing TiO₂-based photocatalytic technology toward practical implementation. This work will provide a comprehensive framework for exploring advanced TiO₂-based composite materials and developing efficient and scalable photocatalytic systems for multifunctional simultaneous hydrogen production.

The global plastic crisis, with over 400 million metric tons produced annually and minimal recycling, demands urgent solutions. Photocatalytic plastic photoreforming offers a dual benefit: converting non-recyclable plastics into hydrogen fuel and valuable chemicals using solar energy under mild conditions. This critical review highlights recent advances in photocatalyst design, including semiconductors, MOF-derived materials, and co-catalyst systems, and explores key insights into plastic degradation mechanisms and reactor configurations. Operational factors such as pH, light intensity, and flow dynamics are discussed for their impact on hydrogen yield and product selectivity. Life cycle and techno-economic assessments reveal current challenges in efficiency, scalability, and cost to illuminate the feasibility of implementing the technology at industrial scale. This study suggests that innovations in catalyst engineering, light management, and system integration provide viable paths forward. With its potential to upcycle plastic waste and contribute to low-carbon hydrogen economies, photoreforming represents a promising approach in advancing circular economy goals, especially when coupled with policy support and smart separation strategies.

Effective pretreatment is essential for achieving long-term stable operation and high water recovery during the desalination of alternative waters. This study developed a process modeling approach for technical, economic, energetic, and environmental assessments of pretreatment technologies to identify the impacts of each technology treating brackish water desalination brine with high scaling propensity. The model simulations evaluated individual pretreatment technologies, including chemical softening (CS), chemical coagulation (CC), electrocoagulation (EC), and ion exchange (IX). In addition, combinations of these pretreatment technologies aiming at the effective reduction of key scaling constituents such as hardness and silica were investigated. The three evaluation parameters in this assessment consist of levelized cost of water (LCOW, $/m³), specific energy consumption and cumulative energy demand (SEC|CED, kWh/m³), and carbon dioxide emissions (CO₂, kg CO_2-eq/m³). The case study evaluated in this work was the desalination brine from the Kay Bailey Hutchison Desalination Plant (KBHDP) with a total dissolved solids (TDS) concentration of 11,000 mg/L and rich in hardness and silica. The evaluation of individual pretreatment units from the highest to lowest LCOW, SEC|CED, and CO₂ emissions in the KBHDP brine was IX > CS > EC > CC, CS > IX > EC > CC, and CC > CS > EC > IX, respectively. In the case of pretreatment combinations for the KBHDP, the EC + IX treatment combination was shown to be the best in terms of the LCOW and CO₂ emissions. The modeling and evaluation of these pretreatment units provide valuable guidance on the selection of cost-effective, energy-efficient, and environmentally sustainable pretreatment technologies tailored to desalination brine applications for minimal- or zero-liquid discharge.