A photovoltaic-electrolysis system with high solar-to-hydrogen efficiency under practical current densities.

Zhang, Qingran; Shan, Yihao; Pan, Jian; Kumar, Priyank; Keevers, Mark J; Lasich, John; Kour, Gurpreet; Daiyan, Rahman et al. · Sci Adv · 2025

basic_science · Level V

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Abstract

The photovoltaic-alkaline water (PV-AW) electrolysis system offers an appealing approach for large-scale green hydrogen generation. However, current PV-AW systems suffer from low solar-to-hydrogen (STH) conversion efficiencies (e.g., <20%) at practical current densities (e.g., >100 mA cm<sup>-2</sup>), rendering the produced H<sub>2</sub> not economical. Here, we designed and developed a highly efficient PV-AW system that mainly consists of a customized, state-of-the-art AW electrolyzer and concentrator photovoltaic (CPV) receiver. The highly efficient anodic oxygen evolving catalyst, consisting of an iron oxide/nickel (oxy)hydroxide (Fe<sub>2</sub>O<sub>3</sub>-NiO<i><sub>x</sub></i>H<i><sub>y</sub></i>) composite, enables the customized AW electrolyzer with unprecedented catalytic performance (e.g., 1 A cm<sup>-2</sup> at 1.8 V and 0.37 kgH<sub>2</sub>/m<sup>-2</sup> hour<sup>-1</sup> at 48 kWh/kgH<sub>2</sub>). Benefiting from the superior water electrolysis performance, the integrated CPV-AW electrolyzer system reaches a very high STH efficiency of up to 29.1% (refer to 30.3% if the lead resistance losses are excluded) at large current densities, surpassing all previously reported PV-electrolysis systems.