Hydrogen spillover inspired bifunctional Platinum/Rhodium Oxide-Nitrogen-Doped carbon composite for enhanced hydrogen evolution and oxidation reactions in base.

The poor activity of Pt-based-catalysts for alkaline hydrogen oxidation/evolution reaction (HOR/HER) encourages scientific society to design an effective electrocatalyst to develop alkaline fuel cells/electrolyzers. Herein, platinum/rhodium oxide-nitrogen-doped carbon (Pt/RhO-CN) composite is prepared for alkaline HER and HOR inspired by hydrogen spillover. The HER performance of Pt/RhO-CN is ∼ 6 times higher than Pt/C. In HOR, Pt/RhO-CN possesses an exchange current density of 657.60 mA/mg, which is ∼ 3.4 times higher than Pt/C. Hydrogen and hydroxyl binding energy (HBE and OHBE) contribute equally to alkaline HOR/HER. The experimental and theoretical evidence suggests that the enhanced HER and HOR activity of Pt/RhO-CN may be due to hydrogen spillover from Pt to RhO. Small work function difference [0.08 eV] of the system suggested hydrogen-spillover is feasible, which has been justified by reaction-free energy calculations. We proposed that the dissociation of hydrogen (H) and water (HO) occurs at Pt to form Pt-adsorbed hydrogen species (Pt-H). Then, some H moves to RhO through hydrogen spillover and reacts with neighboring H or adsorbed hydroxyl species (OH) to form H or HO, which enhances the HER and HOR activity, respectively. The role of water-metal-hydroxyl species in the electrical double layer was also demonstrated on alkaline HOR/HER. This work may help to design the hydrogen-spillover-based catalysts for several renewable energy technologies.