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Adhesion control of various liquid droplets on a liquid-repellent surface is a fundamental technique in novel open channel microfluidic systems. Herein, we demonstrate reversible liquid droplet adhesion switching on superamphiphobic Pd-decorated Ag dendrites (Pd/Ag dendrites).Although adhesion between liquids and the superamphiphobic surfaces was extremely low under ambient air, high adhesion was instantly achieved by exposure of the dendrites to 8% hydrogen gas. Transition from low to high adhesion and the reverse case were successfully repeated more than 10 times by switching from atmospheric ambient air to 8% hydrogen gas. This is the first technique that allows real-time reversible adhesion change with various liquid droplets to a surface using gas-induced structural changes and can potentially be used to realize various functions for droplet-based microfluidics.

The importance of hydrogen peroxide (H 2 O 2 ) continues to grow globally. Deriving the oxygen reduction reaction (ORR) toward the 2epathway to form H 2 O 2 is crucial for high H 2 O 2 productivity. However, most selective electrocatalysts following the 2epathway comprise carbon-containing organic materials with intrinsically low stability, thereby limiting their commercial applicability. Herein, layered double hydroxides (LDHs) are used as inorganic matrices for the first time. The LDH catalyst developed herein exhibits near-100% 2e -ORR selectivity and stably produces H 2 O 2 with a concentration of ≈108.2 mm cm -2 photoanode in 24 h in a two-compartment system (with a photoanode) with a solar-to-chemical conversion efficiency of ≈3.24%, the highest among all reported systems. Density functional theory calculations show that 2e -ORR selectivity is promoted by atomically dispersed cobalt atoms in (012) planes of the LDH catalyst, while a free energy gap between the * O and OOHstates is an important factor.

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