The electro-Fenton (EF) process was first proposed in 1996 and, since then, considerable development has been achieved for its application in wastewater treatment, especially at lab and pilot scale. After more than 25 years, the high efficiency, versatility and environmental compatibility of EF process has been demonstrated. In this review, bibliometrics has been adopted as a tool that allows quantifying the development of EF as well as introducing some useful correlations. As a result, information is summarized in a more visual manner that can be easily analyzed and interpreted as compared to conventional reviewing. During the recent decades under review, 83 countries have contributed to the dramatic growth of EF publications, with China, Spain and France leading the publication output. The top 12 most cited articles, along with the top 32 most productive authors in the EF field, have been screened. Four stages have been identified as main descriptors of the development of EF throughout these years, being each stage characterized by relevant breakthroughs. To conclude, a general cognitive model for the EF process is proposed, including atomic, microscopic and macroscopic views, and future perspectives are discussed.

    Abstract
        Graphical abstract
    1 Introduction
    2 Developments in the EF process in the past two decades
        2.1 Trend in publication of articles in scientific journals
        2.2 Four stages of the EF process development
        2.3 Monitoring the references with strong citation bursts
    3 Conclusions
    4 Future perspectives
    Acknowledgements 
    References

• Fengxia Deng(State Key Laboratory of Urban Water Resources and Environment, School of Environment, Harbin Institute of Technology, Laboratori d’Electroquímica dels Materials i del Medi Ambient, Departament de Ciència de Materials i Química Física, Secció de Química Física, Facultat de Química, Universitat de Barcelona)
• Jizhou Jiang(School of Environmental Ecology and Biological Engineering, Wuhan Institute of Technology)
• Ignasi Sirés(Laboratori d’Electroquímica dels Materials i del Medi Ambient, Departament de Ciència de Materials i Química Física, Secció de Química Física, Facultat de Química, Universitat de Barcelona)