A Self-Supported Ru-Cu₃P Catalyst toward Alkaline Hydrogen Evolution

Transition metal phosphide (TMP) is a kind of effective catalysts toward hydrogen evolution reaction (HER) in alkaline electrolytes. However, the performance of TMP catalysts is strongly limited by water splitting. In this work, we developed a method to prepare a copper foam (CF) supported Ru-doped Cu₃P catalyst (Ru-Cu₃P/CF) by a consecutive growth of Cu(OH)₂ nanoarrays, soaking in RuCl₃ solution and phosphorization. A large surface area was obtained by the self-supported catalysts with the appropriative Ru doping. As an excellent HER catalyst, it exhibited a low overpotential of 95.6 mV at a current density of 10 mA·cm^-2, which is 149.4 mV lower than that of Cu₃P/CF without Ru-doping. The Tafel slope was reduced from 136.6 to 73.6 mA·dec^-1 and the rate determining step was changed from Volmer step to Heyrovsky step. The improvement of HER performance might be attributed to the facilitated water splitting step by Ru-doping, which provides more active sites for water splitting. The nanoparticles morphology of Ru-Cu₃P derived from the Cu(OH)₂ arrays ensured large electrochemical surface areas of the supported electrodes, which could promote the mass and electron transfers, and promote gas production and bubble release. This work highlights the importance of the tuning of the water splitting step and surface engineering by the transition metal with emptier d orbitals, which may pave the road for design of high-performance HER electrocatalyst.