Interconnected hierarchical porous carbon was successfully prepared by direct carbonization of industrial waste sodium lignosulfonate without additional templating and activation agents. The as-prepared carbon sample shows a moderate specific surface area of 903 m² g⁻¹ and high contents of 8.11 at% oxygen and 1.76 at% nitrogen, which could improve the electrolyte-affinitive surface area in an aqueous electrolyte. When used as electrode materials for symmetric supercapacitors in 7 M KOH electrolytes, the as-synthesized carbon sample exhibits a significantly high gravimetric capacitance of 247 F g⁻¹, a volumetric capacitance of 240 F cm⁻³, and an areal capacitance of 27.4 μF cm⁻² at a current density of 0.05 A g⁻¹. Moreover, a superior energy density of 8.4 W h L⁻¹ (at 13.9 W L⁻¹) and a power density of 5573.1 W L⁻¹ (at 3.5 W h L⁻¹), as well as a remarkable cycling stability after 20 000 cycles at two different current densities were achieved for the assembled supercapacitors.

In the context of the increasingly strict pollutant emission regulations and carbon emission reduction targets proposed by the International Maritime Organization, the shipping industry is seeking new types of marine power plants with the advantages of high efficiency and low emissions. Among the possible alternatives, the fuel cell is considered to be the most practical technology, as it provides an efficient means to generate electricity with low pollutant emissions and carbon emissions. Very few comprehensive reviews focus on the maritime applications of the fuel cell. Thus, news reports and literature on the maritime applications of the fuel cell in the past sixty years were collected, and the industrial development status and prospects of the marine fuel cell were summarized as follows. Some countries in Europe, North America and Asia have invested heavily in researching and developing the marine fuel cell, and a series of research projects have achieved concrete results, such as the industrialized marine fuel cell system or practical demonstration applications. At present, the worldwide research of the marine fuel cell focuses more on the proton exchange membrane fuel cell (PEMFC). However, the power demand of the marine fuel cell in the future will show steady growth, and thus the solid oxide fuel cell (SOFC), with the advantages of higher power and fuel diversity, will be the mainstream in the next research stage. Although some challenges exist, the SOFC can certainly lead the upgrading and updating of the marine power system with the cooperative efforts of the whole world.