[Ru(tmphen)][Fe(CN)] and [Ru(phen)][Fe(CN)(NO)] complexes and formation of a heterostructured RuO-FeO nanocomposite as an efficient alkaline HER and OER electrocatalyst.

Water electrolysis is one of the most capable processes for supplying clean fuel. Herein, two novel ionic Ru(II)-Fe(II) complexes, [Ru(tmphen)][Fe(CN)] and [Ru(phen)][Fe(CN)(NO)], where tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline and phen = 1,10-phenanthroline, were synthesized and characterized by UV-Vis spectroscopy, elemental analysis, FT-IR, and single-crystal X-ray structural analysis. By thermally decomposing the [Ru(tmphen)][Fe(CN)] complex at 600 °C for 4 h, a heterostructured RuO-FeO nanocomposite was fabricated through a facile one-pot treatment and then characterized by FT-IR, XRD, FT-Raman, UV-Vis (DRS), ICP-OES, FE-SEM, TEM, TGA/DTG, BET, and XPS analyses, which revealed the formation of highly crystalline RuO-FeO nanoparticles with an average size of 8-12 nm. The prepared nanocomposite was an efficient heterostructured electrocatalyst for performing water-splitting redox reaction processes, including hydrogen and oxygen evolution reactions (HER and OER) in alkaline solutions. In this regard, RuO and FeO samples were also prepared through thermal decomposition of Ru(tmphen) and K[Fe(CN)] precursors, respectively, as control experiments to compare their HER and OER electrocatalytic activity with that of the RuO-FeO nanocomposite. Specifically, the RuO-FeO nanocomposite exhibited significant electrocatalytic performance, generating 10 mA cm current density at -148 and 292 mV overpotentials, and the Tafel slope results from fitting the LSV curves to the Tafel equation were -43 and 56.08 mV dec for the HER and OER, respectively. Therefore, the heterostructured RuO-FeO nanocomposite can be viewed as a bi-functional electrocatalyst for HER and OER because it exploits the synergistic effects of heterostructures and active sites at its interface.