Technological change as evolving citation networks: The analysis of proton exchange membrane fuel cell

Proton exchange membrane fuel cell (PEMFC) is the dominant fuel cell technology in terms of system shipments. Although the applications of the technology have already been on the market for several years, efforts to improve its performance, cost, and stability continues. There have been around 500 PEMFC research articles published every year recently. As the first step of a longer term effort to systematically detecting technological changes, this study selects PEMFC as the target technology to visualize its technological development and uncovers its recent research fronts. We collect PEMFC research articles from the Web of Science database and establish a citation network using the associated citation information. Main PEMFC development paths are uncovered through key-route main path analysis. The main path results show that modeling is the main focus of PEMFC technology development which evolves from simple to more complicated structures and from static to transient phenomena. The citation network is further separated into groups using the Girvan-Newman edge-betweenness clustering method, which successfully identifies ten groups of articles with strong internal coherence. These groups can be regarded as the research fronts of the technology.