A fundamental understanding of the origin of oxygen evolution reaction (OER) activity of transition-metal-based electrocatalysts, especially for single precious metal atoms supported on layered double hydroxides (LDHs), is highly required for the design of efficient electrocatalysts toward further energy conversion technologies. Here, we aim toward single-atom Au supported on NiFe LDH (Au/NiFe LDH) to clarify the activity origin of LDHs system and a 6-fold OER activity enhancement by 0.4 wt % Au decoration. Combining with theoretical calculations, the active behavior of NiFe LDH results from the in situ generated NiFe oxyhydroxide from LDH during the OER process. With the presence ofAu, Au/NiFe LDH possesses an overpotential of 0.21 V in contrast to the calculated result (0.18 V). We ascribe the excellent OER activity ofAu/NiFe LDH to the charge redistribution of active Fe as well as its surrounding atoms causing by the neighboring Au on NiFe oxyhydroxide stabilized by interfacial CO and HO interfacing with LDH.

Harvesting heat from the environment into electricity has the potential to power Internet-of-things (IoT) sensors, freeing them from cables or batteries and thus making them especially useful for wearable devices. We demonstrate a giant positive thermopower of 17.0 millivolts per degree Kelvin in a flexible, quasi-solid-state, ionic thermoelectric material using synergistic thermodiffusion and thermogalvanic effects. The ionic thermoelectric material is a gelatin matrix modulated with ion providers (KCl, NaCl, and KNO3) for thermodiffusion effect and a redox couple [Fe(CN)64–/Fe(CN)63–] for thermogalvanic effect. A proof-of-concept wearable device consisting of 25 unipolar elements generated more than 2 volts and a peak power of 5 microwatts using body heat. This ionic gelatin shows promise for environmental heat-to-electric energy conversion using ions as energy carriers.

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