Sonolytic and ultrasound-assisted hydrogen production: insights, trends, and future perspectives

• Research in ultrasound-assisted H 2 evolved rapidly from 2000 to 2025. • HER optimization via sonocatalysis with g-C 3 N 4 , TiO 2 , and quantum dots. • Trends show rising interest in piezocatalysis and biohydrogen pathways. • Hybrid systems link sonochemistry with photo-, electro-, and thermocatalysis. • China leads globally, with India, Korea, and others expanding collaboration. This study employs the bibliometric review method to assess the evolution of research in sonolytic and ultrasound-assisted hydrogen production between 2000 and 2025 using data from the Scopus database. The study found research done so far as a dynamic, cross-disciplinary field driven by global decarbonization and technological innovation. Keyword and thematic mapping identified a central focus towards maximizing the hydrogen evolution reaction (HER) with the assistance of ultrasound catalysis, with advanced materials like g-C 3 N 4 , TiO 2 , and quantum dots. Emerging themes of piezocatalysis, biohydrogen, and ultrasonication-enhanced pretreatment indicate a trend towards multifunctional, sustainable, and bio-integrated processes. The clustering analysis identified distinct strategic research directions, including visible-light-driven heterojunctions, anticorrosion electrodes, ultrasonic fermentation, and hybrid catalytic systems integrating sonochemistry with photocatalysis, electrocatalysis, and thermochemical reforming. Non-noble metal catalysts and nanostructures enabled by sonication are especially gaining prominence owing to their efficiency and scalability. The country-level analysis revealed a commanding position for China, with growing contributions from India, South Korea, and strategic international collaborations. Together, the field is transitioning from fundamental research to application-oriented innovation, and the future opportunity rests in scalable, hybrid systems that integrate ultrasonic, optical, and biochemical processes. These findings suggest that ultrasound-assisted hydrogen generation may contribute to advances in sustainable energy technologies and potential industrial implementation.