Gallium Nitride‐Based Electrode Materials for Supercapacitors: From Wide Band Semiconductor to Energy Storage Platform

ABSTRACT Gallium Nitride (GaN) is transforming power electronics and optoelectronics; not only that, but it is also quickly becoming a primary component of the new generation of supercapacitors. GaN is a unique material that combines excellent electrochemical stability and tunable nanostructures with the best electrical properties. This review analyzes recent developments in GaN‐based supercapacitor technology, emphasizing the rationale behind the increased research in this area and presenting the main challenges. The enhancement of the field of pure and porous GaN to more elaborate hybrids, including GaN with carbon materials, or transition metal oxides or nitrides, or doping with some metal. The main parameters that have been summarized here include specific capacitance up to 1915.5 mF cm −2 , energy and power density up to 13.3 mWh cm −2 and 1000 mW cm −3 , and cycle stability remains high at 99 % despite 10 000–50 000 cycles. Chemical view brings together the connections between the different methods of synthesis, which include Chemical Vapor Deposition (CVD), hydrothermal processes, and electrochemical etching, and how these have been applied to affect electrochemical performance. When comparisons are made between electrodes, electrolytes, and device designs, then a better understanding of how GaN accumulates charge and which factors deplete it is achieved.