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

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 −2 ), rendering the produced H 2 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 2 O 3 -NiO x H y ) composite, enables the customized AW electrolyzer with unprecedented catalytic performance (e.g., 1 A cm −2 at 1.8 V and 0.37 kgH 2 /m −2 hour −1 at 48 kWh/kgH 2 ). 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.