Yongchao Yao

Abstract Seawater electroreduction is attractive for future H 2 production and intermittent energy storage, which has been hindered by aggressive Mg 2+ /Ca 2+ 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 H 2 bubbles to almost every corner of the cathode to repel Mg 2+ /Ca 2+ 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 H 2 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% H 2 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 ).

Abstract Seawater electrolysis is an attractive way of making H 2 in coastal areas, and NiFe‐based materials are among the top options for alkaline seawater oxidation (ASO). However, ample Cl − in seawater can severely corrode catalytic sites and lead to limited lifespans. Herein, we report that in situ carbon oxyanion self‐transformation (COST) from oxalate to carbonate on a monolithic NiFe oxalate micropillar electrode allows safeguard of high‐valence metal reaction sites in ASO. In situ/ex situ studies show that spontaneous, timely, and appropriate COST safeguards active sites against Cl − attack during ASO even at an ampere‐level current density ( j ). Our NiFe catalyst shows efficient and stable ASO performance, which requires an overpotential as low as 349 mV to attain a j of 1 A cm −2 . Moreover, the NiFe catalyst with protective surface CO 3 2− exhibits a slight activity degradation after 600 h of electrolysis under 1 A cm −2 in alkaline seawater. This work reports effective catalyst surface design concepts at the level of oxyanion self‐transformation, acting as a momentous step toward defending active sites in seawater‐to‐H 2 conversion systems.

Abstract Renewable electricity‐powered nitrate/carbon dioxide co‐reduction reaction toward urea production paves an attractive alternative to industrial urea processes and offers a clean on‐site approach to closing the global nitrogen cycle. However, its large‐scale implantation is severely impeded by challenging C–N coupling and requires electrocatalysts with high activity/selectivity. Here, cobalt‐nanoparticles anchored on carbon nanosheet (Co NPs@C) are proposed as a catalyst electrode to boost yield and Faradaic efficiency (FE) toward urea electrosynthesis with enhanced C–N coupling. Such Co NPs@C renders superb urea‐producing activity with a high FE reaching 54.3% and a urea yield of 2217.5 µg h −1 mg cat. −1 , much superior to the Co NPs and C nanosheet counterparts, and meanwhile shows strong stability. The Co NPs@C affords rich catalytically active sites, fast reactant diffusion, and sufficient catalytic surfaces‐electrolyte contacts with favored charge and ion transfer efficiencies. The theoretical calculations reveal that the high‐rate formation of *CO and *NH 2 intermediates is crucial for facilitating urea synthesis.