“…Overexploitation of coal, petroleum, natural gas, and other traditional fossil energy has caused a severe energy dilemma and environmental pollution. − Thus, developing an efficient, low-cost, and clean energy system globally is the primary challenge for replacing the above fossil fuels. − With the introduction of the concept of carbon neutralization, many countries in the world have taken steps to promote the conversion and application of renewable energy, including hydropower, tide, solar, and hydrogen energy. − Compared with other alternative energy sources, hydrogen (H 2 ) is a clean energy carrier with abundant storage, highly cost-effective, and carbon-free characteristics . The water splitting technique is an efficient way driven by renewable energy, such as wind and solar, to produce high-purity H 2 . − Electrocatalytic water splitting is a hot spot and challenge in current scientific research, which is also the core issue that needs to be solved in the research program of green energy H 2 production. Figure shows the whole process of the hydrogen energy system by electrocatalytic water splitting, including the device of water splitting, utilization of renewable energy, and several applications of the generated H 2 .…”