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This study presents a bibliometric review focusing on the utilization of water electrolysis as a means of generating hydrogen as an energy carrier. The analysis includes research conducted over the past decade, covering from 2014 to 2023 (till August). Several key aspects are highlighted, including publication trends, the leading country in research output, journal rankings, and a citation analysis of papers related to water electrolysis. The findings reveal a notable increase in publication trends, with China emerging as the leading contributor in this research area. Furthermore, the International Journal of Hydrogen Energy is identified as the highest-ranked journal in terms of both publication number and citation impact. Additionally, the top ten most cited research articles and review papers are investigated to determine their influence within the field. To gain a deeper understanding of water electrolysis methods, the three primary approaches: alkaline water electrolysis (AWE), proton exchange membrane (PEM) electrolysis, and solid oxide electrolysis (SOE) is examined. The analysis emphasizes that PEM electrolysis is the most prevalent method for hydrogen generation, particularly when integrated with renewable energy sources such as solar and wind power due to its rapid response to electrical input fluctuation. Finally, the challenges and future directions of water electrolysis in hydrogen production are highlighted, including an exploration of economic and environmental considerations at large scale, offering insights into the path forward for advancing this technology sustainably. • A comprehensive bibliometric analysis of water electrolysis for hydrogen production. • Publication trends, journal rankings, and citation analysis are highlighted. • China is identified as the leading contributor in water electrolysis publications. • International Journal of Hydrogen Energy: the highest-ranked journal in this field. • Specific electrolysis methods, including AWE, PEM, and SOE are examined. [ABSTRACT FROM AUTHOR]

The production of energy, food, water, and other utensils by fossil fuels generates pollution that causes constant climate change. To minimize and avoid this phenomenon, opting for less polluting energy production sources is increasingly necessary. Green hydrogen (H 2), a renewable and clean fuel, is analyzed in bibliometric terms in the present work, emphasizing photosynthetic H 2. The data were obtained through the journal database list in Web of Science, in which a total of 1507 was published between January 2010 to September 2022, dealing with the production of photosynthetic green hydrogen. The country with the most significant publication is China, with respectively 24.50% of the publications, and the Chinese Academy of Sciences has 60 co-authored papers, the largest in co-authorship—most papers published in the international journal of hydrogen energy, with 19.49% of the publications. The raw materials identified as emerging are cyanobacteria and microalgae, Rhodobacter capsulatus , synechocystis sp pcc6803 and Chlamydomonas reinhardtii pointed out as the microalgae of most significant interest. However, it is necessary to improve them, given the decrease in inactivity provided by the Calvin-Benson cycle. Life cycle assessment studies are needed, as well as H 2 storage. There is a need to reduce the levelized cost of H 2 production, which is around 9.65–25.22 USD/gallon. Studies also point to using cyanobacteria and microalgae to produce other biofuels (bioethanol biodiesel) and materials (supercapacitors, batteries, and polymers). [Display omitted] • Evaluation of the photosynthetic production of green hydrogen. • Analysis of 1507 papers from the Web of Science with CiteSpace, Vosviwer and Exell. • Advanced bibliometric analysis of future trends in the production of green hydrogen. • Using photosynthetic methods to produce biofuels. • Polymer production uses carbon dioxide and green hydrogen. [ABSTRACT FROM AUTHOR]

Based on literature research, this comprehensive analysis of 1275 articles published in the past five decades provides quantitative and objective insight into research trends in the hydrogen economy. Scholars and experts agree that by 2030, hydrogen will play a critical role in energy transition by complementing other renewable energy technologies. We applied indicators such as the Field-Weighted Citation Impact index, cited by and usage count (180 days) to evaluate countries, authors, documents, journals and so on. We also used VOS viewer to visualize the evolving trend using keyword analysis and cluster analysis of documents. Results show that the literature on the hydrogen economy has been recently increasing, particularly from 2016 to 2020. Scopus database was employed to acquire the required data for the study. From preliminary analysis, it was established that from 218 journals, 1275 documents related to hydrogen economy had been published so far. The average publication per year since introducing the term "hydrogen economy" is 6.62 and increasing. The average citation per document is 47.21. There have been 3760 authors so far who have been associated with publications related to a hydrogen economy. Of which 139 authors have written 156 documents individually, and 3621 authors have collaborated to publish 1119 documents, thus forming a collaborative index of 3.24. The International Journal of Hydrogen Energy contributes 40% of the overall publications. In terms of countries, China and United States are the leaders, with 126 papers each. Our analysis shows that the study on hydrogen economy mostly deals with multidisciplinary aspects like hydrogen production, storage, transportation, application, and public policy formulation. We adopted the 180 days usage count offered by the Web of Science database to better understand the research hotspot and evolving trends. It helped us view the existing gaps and potential scope of study that future researchers working on the hydrogen economy can explore. Aspects like pipeline transportation, risk assessment studies, blending, public safety and hazard mitigation can play a vital role in the hydrogen economy research in the future. Cooperation between nations and research institutes should be fostered with cross-disciplinary interchange to boost the hydrogen economy's multidisciplinary growth. • Bibliometric analysis reveals International Journal of Hydrogen Energy is the pioneer journal on hydrogen economy. • Network visualisation analyses disclose that there is a high collaboration index (3.24) among authors. • USA and China are the leaders with 10% publication each. • Emphasis is needed on pipeline transportation, risk assessment studies, and hydrogen blending research. • Hydrogen supply chain and hydrogen fuel cell were the prime themes. [ABSTRACT FROM AUTHOR]

Based on literature research, this comprehensive analysis of 1275 articles published in the past five decades provides quantitative and objective insight into research trends in the hydrogen economy. Scholars and experts agree that by 2030, hydrogen will play a critical role in energy transition by complementing other renewable energy technologies. We applied indicators such as the Field-Weighted Citation Impact index, cited by and usage count (180 days) to evaluate countries, authors, documents, journals and so on. We also used VOS viewer to visualize the evolving trend using keyword analysis and cluster analysis of documents. Results show that the literature on the hydrogen economy has been recently increasing, particularly from 2016 to 2020. Scopus database was employed to acquire the required data for the study. From preliminary analysis, it was established that from 218 journals, 1275 documents related to hydrogen economy had been published so far. The average publication per year since introducing the term "hydrogen economy" is 6.62 and increasing. The average citation per document is 47.21. There have been 3760 authors so far who have been associated with publications related to a hydrogen economy. Of which 139 authors have written 156 documents individually, and 3621 authors have collaborated to publish 1119 documents, thus forming a collaborative index of 3.24. The International Journal of Hydrogen Energy contributes 40% of the overall publications. In terms of countries, China and United States are the leaders, with 126 papers each. Our analysis shows that the study on hydrogen economy mostly deals with multidisciplinary aspects like hydrogen production, storage, transportation, application, and public policy formulation. We adopted the 180 days usage count offered by the Web of Science database to better understand the research hotspot and evolving trends. It helped us view the existing gaps and potential scope of study that future researchers working on the hydrogen economy can explore. Aspects like pipeline transportation, risk assessment studies, blending, public safety and hazard mitigation can play a vital role in the hydrogen economy research in the future. Cooperation between nations and research institutes should be fostered with cross-disciplinary interchange to boost the hydrogen economy's multidisciplinary growth. • Bibliometric analysis reveals International Journal of Hydrogen Energy is the pioneer journal on hydrogen economy. • Network visualisation analyses disclose that there is a high collaboration index (3.24) among authors. • USA and China are the leaders with 10% publication each. • Emphasis is needed on pipeline transportation, risk assessment studies, and hydrogen blending research. • Hydrogen supply chain and hydrogen fuel cell were the prime themes. [ABSTRACT FROM AUTHOR]

Hydrogen is a promising sustainable energy carrier for the future due to its high energetic content and no emissions, other than water vapor. However, its full deployment still requires technological advances in the renewable and cost-effective production of hydrogen, cost reduction of fuel cells and especially in the storage of hydrogen in a lightweight, compact and safe manner. One way to achieve this is by using materials in which hydrogen bonds chemically, or by adsorption. Different kinds of Hydrogen Storage Materials have been investigated, such as Metal-Organic Frameworks (MOFs), Simple Hydrides (including Magnesium Hydride, MgH 2), AB 5 Alloys, AB 2 Alloys, Carbon Nanotubes, Graphene, Borohydrides, Alanates and Ammonia Borane. Billions have been invested in Storage Materials research, resulting in tens of thousands of papers. Thus, it is challenging to track how much effort has been devoted to each materials class, by which countries, and how the field has evolved over the years. Quantitative Science and Technology Indicators, produced by applying Bibliometrics and Text Mining to scientific papers, can aid in achieving this task. In this work, we evaluated the evolution and distribution of Hydrogen Storage Materials research using this methodology. Papers in the 2000–2015 period were collected from Web of Science and processed in VantagePoint® bibliometric software. A thesaurus was elaborated relating keywords and short phrases to specific Hydrogen Storage Materials classes. The number of publications in Hydrogen Storage Materials grew markedly from 2003 to 2010, reducing the pace of growth afterwards until a plateau was reached in 2015. The most researched materials were MOFs, Simple Hydrides and Carbon-based materials. There were three typical trends in materials classes: emerging materials, developed after 2003, such as MOFs and Borohydrides; classical materials with continuous growth during the entire period, such as Simple Hydrides; and stagnant or declining materials, such as Carbon Nanotubes and AB 5 Alloys. The main publishing countries were China, countries from the European Union (EU) and the USA, followed by Japan. There is a division between countries with continued growth in recent years, such as China, and those with stagnant production after 2010, such as the EU, the USA and Japan. The results of this work, compared to a previous study in storage materials patenting by our group, and the recent launch of commercial hydrogen cars and trains and stationary hydrogen production and fuel cell solutions, indicates that although the Hydrogen Energy field as a whole is transitioning from lab and prototype stages to commercial deployment, materials-based hydrogen storage still has base technological challenges to be overcome, and therefore still needs more scientific research before large scale commercialization can be realized. The developed thesaurus is made available for refinement and future works. • H 2 storage materials papers grew exponentially between 2000 and 2009, and maxed in 2015. • Most researched classes: MOFs, Simple Hydrides and Carbon-based materials. • US, EU and JP topped in 2009, while CN, KR and AU continued growing. [ABSTRACT FROM AUTHOR]