Abstract
Hydrogen (H(2)) production is a latent feasibility of renewable clean energy. The industrial H(2) production is obtained from reforming of natural gas, which consumes a large amount of nonrenewable energy and simultaneously produces greenhouse gas carbon dioxide. Electrochemical water splitting is a promising approach for the H(2) production, which is sustainable and pollution-free. Therefore, developing efficient and economic technologies for electrochemical water splitting has been an important goal for researchers around the world. The utilization of green energy systems to reduce overall energy consumption is more important for H(2) production. Harvesting and converting energy from the environment by different green energy systems for water splitting can efficiently decrease the external power consumption. A variety of green energy systems for efficient producing H(2), such as two-electrode electrolysis of water, water splitting driven by photoelectrode devices, solar cells, thermoelectric devices, triboelectric nanogenerator, pyroelectric device or electrochemical water-gas shift device, have been developed recently. In this review, some notable progress made in the different green energy cells for water splitting is discussed in detail. We hoped this review can guide people to pay more attention to the development of green energy system to generate pollution-free H(2) energy, which will realize the whole process of H(2) production with low cost, pollution-free and energy sustainability conversion.