Identifying Key Design Criteria for Large-Scale Photocatalytic Hydrogen Generation from Engineering and Economic Perspectives
Cui Ying Toe, Jian Pan, Jason Scott, Rose Amal
Abstract
Photocatalytic hydrogen (H2) generation has emerged as a promising approach for direct conversion of solar energy into green H2 fuel. Prior works predominantly focused on photocatalyst material development and optimization with photoreactor and system design receiving considerably less attention. Further, significantly less focus has been devoted to the economic feasibility study of photoreactor systems. Therefore, this Perspective contemplates photoreactor design and scale up from an economic viewpoint. The economics of two popular large-scale photoreactor designs, (i) panel and (ii) slurry based, are evaluated. This Perspective suggests that the design of a photocatalytic slurry system is approximately 12% more cost effective than a panel photoreactor system under the base-case scenario in producing 10 kg H2/day. The analysis also suggests that a cost reduction of up to 75% can be achieved if the photon conversion efficiency is increased from 1% to 5%, indicating that research and development should continue to be undertaken to increase process efficiency via photocatalyst and system engineering. In addition, other considerations, such as improving photocatalyst reusability (to give a photocatalyst lifespan of at least 1 year), reducing photocatalyst cost (using non-noble-metal-based photocatalysts) and increasing input photon density (installing a solar concentrator to harness more than 1 Sun intensity), will each impose an additional 20–30% of the cost.