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Bidirectional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts are key for molecular oxygen-centric renewable energy transduction via metal-air batteries. Here, a molecular cobalt complex is covalently tethered on a strategically functionalized silica surface that displayed both ORR and OER in alkaline media. The detailed X-ray absorbance spectroscopy (XAS) studies indicate that this catalyst retains its intrinsic molecular features while playing a central role during bidirectional electrocatalysis and demonstrating a relatively lower energy gap between O 2 /H 2 O interconversions. This robust molecular catalyst-silica composite (deposited on a porous carbon paper) is assembled along with a zinc foil and polymeric gel membrane to devise an active single-stack quasi-solid zinc-air battery (ZAB) setup. This quasi-solid ZAB assembly displayed impressive power density (60 mW cm -2 @100 mA cm -2 ), specific capacity (818 mAh g -1 @ 5mA cm -2 ), energy density (757 Whkg -1 @5mA cm -2 ), and elongated charging/discharging life (28 h). An appropriate assembly of these ZAB units is able to power practical electronic appliances, requiring ≈1.6-6.0V potential requirements., (© 2024 Wiley‐VCH GmbH.)

This work illustrates the practicality and economic benefits of employing a hetero-interfaced electrocatalyst (CoS 2 @CoFe-LDH), containing cobalt sulphide and iron-cobalt double-layer hydroxide for large-scale hydrogen generation. Here, the rational synthesis and detailed characterization of the CoS 2 @CoFe-LDH material to unravel its unique heterostructure are essayed. The CoS 2 @CoFe-LDH operates as a bifunctional electrocatalyst to trigger both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline seawater (pH 14.0) while showcasing low overpotential requirement for HER (311 mV) and OER (450 mV) at 100 mA cm - 2 current density. The identical CoS 2 @CoFe-LDH on either electrode in an H-cell setup results in simultaneous H 2 and O 2 production from seawater with a ≈98% Faradaic efficiency with an applied potential of 1.96V@100 mA cm - 2 . Next, this CoS 2 @CoFe-LDH catalyst is deployed on both sides of a membrane electrode assembly in a one-stack electrolyzer, which retains the intrinsic bifunctional reactivity of the catalyst to generate H 2 and O 2 in tandem from alkaline seawater with an impeccable energy efficiency (50 kWh kg -1 -of-H 2 ). This electrolyzer assembly can be directly linked with a Si-solar cell to produce truly green hydrogen with a solar-to-hydrogen generation efficiency of 15.88%, highlighting the potential of this converting seawater to hydrogen under solar irradiation., (© 2024 Wiley‐VCH GmbH.)