A review is given of the exceptional electrochemical performance of epitaxial InN/InGaN quantum dots(QDs) as photoelectrodes for solar hydrogen generation by water spliting, as biosensor transducers and as anion-selective electrodes, and they are also evaluated as supercapacitor electrodes. he performance is benchmarked against the best performances of other reported materials and nanostructures. A model based on the unique interplay of surface and quantum properties is put forward to understand the boost of catalytic activity and anion selectivity interlinking quantum nanostructure physics with electrochemistry and catalysis. Of equal impact is the direct growth on cheap Si substrates without any bufer layers, allowing novel device designs and integration with Si technology. his makes the InN/InGaN QDs viable, opening up new application ields for Ⅲ-nitride semiconductors. A review is given of the exceptional electrochemical performance of epitaxial InN / InGaN quantum dots (QDs) as photoelectrodes for solar hydrogen generation by water spliting, as biosensor transducers and as anion-selective electrodes, and they are also evaluated as supercapacitor electrodes. is benchmarked against the best performances of other reported materials and nanostructures. A model based on the unique interplay of surface and quantum properties is put forward to understand the boost of catalytic activity and anion selectivity interlinking quantum nanostructure physics with electrochemistry and catalysis. Of equal impact is the direct growth on cheap Si substrates without any bufer layers, allowing novel device designs and integration with Si technology. his makes the InN / InGaN QDs viable, opening up new applications ields for III-nitride semiconductors.