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.