Hydrogen storage and delivery: immobilization of a highly active homogeneous catalyst for the decomposition of formic acid to hydrogen and carbon dioxide

The homogeneous catalytic system, based on water-soluble ruthenium(II)–TPPTS catalyst (TPPTS = meta-trisulfonated triphenylphosphine), selectively decomposes HCOOH into H₂ and CO₂ in aqueous solution. Although this reaction results in only two gas products, heterogeneous catalysts could be advantageous for recycling, especially for dilute formic acid solutions, or for mobile, portable applications. Several approaches have been used to immobilize/solidify the homogeneous ruthenium–TPPTS catalyst based on ion exchange, coordination and physical absorption. The activity of the various heterogeneous catalysts for the decomposition of formic acid has been determined. These heterogenized catalysts offer the advantage of easy catalyst separation/recycling in dilute formic acid, or for mobile, portable applications.