Efficient bubble/precipitate traffic enables stable seawater reduction electrocatalysis at industrial-level current densities

Seawater electroreduction is attractive for future H₂ production and intermittent energy storage, which has been hindered by aggressive Mg²⁺/Ca²⁺ precipitation at cathodes and consequent poor stability. Here we present a vital microscopic bubble/precipitate traffic system (MBPTS) by constructing honeycomb-type 3D cathodes for robust anti-precipitation seawater reduction (SR), which massively/uniformly release small-sized H₂ bubbles to almost every corner of the cathode to repel Mg²⁺/Ca²⁺ precipitates without a break. Noticeably, the optimal cathode with built-in MBPTS not only enables state-of-the-art alkaline SR performance (1000-h stable operation at -1 A cm^-2) but also is highly specialized in catalytically splitting natural seawater into H₂ with the greatest anti-precipitation ability. Low precipitation amounts after prolonged tests under large current densities reflect genuine efficacy by our MBPTS. Additionally, a flow-type electrolyzer based on our optimal cathode stably functions at industrially-relevant 500 mA cm^-2 for 150 h in natural seawater while unwaveringly sustaining near-100% H₂ Faradic efficiency. Note that the estimated price (~1.8 US$/kg_H2) is even cheaper than the US Department of Energy's goal price (2 US$/kg_H2).