Surface modification of hydroxyapatite for hydrogen generation

Hydrogen provides a safe and clean alternative to carbon-based fuels. Having the proper catalytic support for production of hydrogen is a valuable technology. We report on the surface modification of hydroxyapatite as a novel catalytic support material for hydrogen generation. Aside from being inexpensive and durable, we reveal that Ru ion exchange on the HAP surface provides a highly active support for sodium borohydride hydrolysis, exemplifying a high total turnover number on the order of 24,000 mol H2/mol Ru. Moreover, we observe that the RuHAP support exhibits a long catalytic lifetime of approximately 1 month upon repeated exposure to NaBH4 solutions. We identified the ability of complex surface morphology to enhance hydrolysis by the catalytic transition metal covered surface. Particularly, we found that the complex morphology of polycrystalline RuHAP catalytic supports exhibits shorter induction times for hydrogen generation as well as improved reaction rates as compared with single crystal supports possessing the same Ru content. By decreasing induction time and enhancing catalytic activity, we find it feasible to further explore this catalyst support in the construction of a practical hydrogen generation system.

Graphical abstractThe ion exchange of ruthenium onto a hydroxyapatite surface provided a novel catalytic support for hydrogen generation, exhibiting long catalytic lifetime and especially high rates of hydrolysis for polycrystalline morphologies.Figure optionsDownload full-size imageDownload high-quality image (97 K)Download as PowerPoint slideHighlights► First use of Ru hydroxyapatite as a catalytic support material for H2 generation. ► H2 generation rate increased using support with complex surface morphology. ► Induction time shortened using support with complex surface morphology. ► High total turnover number for hydrogen generation of 24,000 mol H2/mol Ru. ► Long catalytic lifetime of 1 month demonstrated by amorphous catalytic support.