High-performance alkaline water electrolyzers based on Ru-perturbed Cu nanoplatelets cathode.

Alkaline electrolyzers generally produce hydrogen at current densities below 0.5 A/cm 2 . Here, we design a cost-effective and robust cathode, consisting of electrodeposited Ru nanoparticles (mass loading ~ 53 µg/cm 2 ) on vertically oriented Cu nanoplatelet arrays grown on metallic meshes. Such cathode is coupled with an anode based on stacked stainless steel meshes, which outperform NiFe hydroxide catalysts. Our electrolyzers exhibit current densities as high as 1 A/cm 2 at 1.69 V and 3.6 A/cm 2 at 2 V, reaching the performances of proton-exchange membrane electrolyzers. Also, our electrolyzers stably operate in continuous (1 A/cm 2 for over 300 h) and intermittent modes. A total production cost of US$2.09/kg H2 is foreseen for a 1 MW plant (30-year lifetime) based on the proposed electrode technology, meeting the worldwide targets (US$2-2.5/kg H2 ). Hence, the use of a small amount of Ru in cathodes (~0.04 g Ru per kW) is a promising strategy to solve the dichotomy between the capital and operational expenditures of conventional alkaline electrolyzers for high-throughput operation, while facing the scarcity issues of Pt-group metals.