A Stable Integrated Photoelectrochemical Reactor for H₂ Production from Water Attains a Solar‐to‐Hydrogen Efficiency of 18 % at 15 Suns and 13 % at 207 Suns

Abstract

The major challenge in solar water splitting to H2 and O2 is in making a stable and affordable system for large‐scale applications. We have designed, fabricated, and tested a photoelectrochemical reactor characterized as follows: 1) it comprises an integrated device to reduce the balance of the system cost, 2) it utilizes concentrated sunlight to reduce the photoabsorber cost, and 3) it employs and alkaline electrolyte to reduce catalyst cost and eliminate external thermal management needs. The system consists of an III‐V‐based photovoltaic cell integrated with Ni foil as an O2 evolution catalyst that also protects the cell from corrosion. At low light concentration, without the use of optical lenses, the solar‐to‐hydrogen (STH) efficiency was 18.3 %, while at high light concentration (up to 207 suns) with the use of optical lenses, the STH efficiency was 13 %. Catalytic tests conducted for over 100 hours at 100–200 suns showed no sign of degradation nor deviation from product stoichiometry (H2/O2=2). Further tests projected a system stability of years.

A Review of Inorganic Photoelectrode Developments and Reactor Scale‐Up Challenges for Solar Hydrogen Production

“…integrated a triple‐junction GaInP/GaInAs/Ge photovoltaic within a PEC reactor. [ 161,162 ] Ni foil was affixed to the Ge side of the photovoltaic, which drove the water oxidation reaction in solution. The GaInP side was wired to a Pt‐coated Ti mesh, which drove the water reduction reaction.…”

How much technological progress is needed to make solar hydrogen cost-competitive?

“…Producing green hydrogen at a cost that is competitive with fossil fuel-derived hydrogen is one of the major challenges for transitioning to a hydrogen economy. [1] There are promising technologies for converting solar energy and water to hydrogen, such as coupling of photovoltaic and electrolysis (PV+E), [2] photoelectrochemical (PEC) [3,4] and (particulate) photocatalytic (PC) [5] water splitting (see Figure 1). These technologies, however, cannot currently produce hydrogen at a cost that is competitive with hydrogen derived from steam reforming.…”

“…Irradiation of the PEC cells leads to hydrogen and oxygen production on opposites sides of cell, so that pure hydrogen can be obtained (see Figure 1, PEC). State-of-the-art properties of the PEC cells are based on devices by Kistler et al [3] and Khan et al [4] using a III-V absorber. The layout of the hydrogen production plant is based on Pinaud et al (type 4 -PEC).…”

“…Hence, scaling and geographical effects on the LCOH2 are not considered. 4. In this study, only a cost analysis of hydrogen production is performed.…”

Toward Large‐Scale Hydrogen Production from Water: What Have We Learned and What Are the Main Research Hurdles to Cross for Commercialization?

“…The stability issues related to the back side of the cells has been addressed as shown in Figure 2 . It was found that a Ni foil connected to the back side protects it from corrosion and depending on its thickness and extracted current this can extend to many years (more details can be found in Khan et al [ 63 ] ). At present, the practice is to protect the front side (the side receiving light) with a poly(methyl methacrylate) (PMMA) window and extract the generated electrons toward a cathode (the loss is ≈6% of the photons’ flux in this case).…”