Efficient electrocatalytic H2O2 production in simulated seawater on ZnO/reduced graphene oxide nanocomposite

The non-noble metal-based catalysts has been widely studied for two-electron (2e-) oxygen reduction reaction (ORR), and exhibited the excellent 2e- ORR performance in alkaline condition, especially. However, these catalysts are rarely studied at neutral chloride medium. Herein, we synthesized metal oxide nanoparticles supported reduced graphene oxide composites (MxOy/rGO) by adding the precursors of metal salts (Zn, Mn, Co and Fe) and graphene oxide (GO) through a facile lyophilization-pyrolysis strategy. ZnO/rGO exhibits a well 2e- ORR catalytic activity, corresponding to a high 80% H2O2 selectivity and preferable stability in 0.5 M NaCl solution, whereas the MxOy/rGO (M= Mn, Co and Fe) presents even lower selectivity than reduced graphene oxide (rGO). The results suggest that ZnO promotes the 2e- ORR, and the metal oxide (M= Mn, Co and Fe) conducive to 4e- ORR. Interesting finding, the results of rotating ring disk electrode (RRDE) show that chloride ion in the electrolyte promote the H2O2 selectivity of 2e- ORR. These findings provide a promising candidate material for 2e- ORR in neutral chloride environment and valuable insights for future research on seawater-based H2O2 electrosynthesis.