Short-range order in amorphous nickel oxide nanosheets enables selective and efficient electrochemical hydrogen peroxide production

Achieving high selectivity and activity with the oxygen reduction reaction (ORR) is significant for developing efficient energy conversion techniques and chemical production. Here, we report that selective ORRs can be achieved by tuning short-range order in amorphous and crystalline NiO nanosheets (a-NiO NSs and c-NiO NSs, respectively). X-ray absorption spectroscopy analysis reveals that the short-range order of a-NiO NSs and c-NiO NSs mainly adopt the NiO5 pyramidal and NiO6 octahedral structures, respectively. The a-NiO NSs for electrochemical H2O2 production in 0.1 M KOH exhibits both high selectivity over 90% and high activity (1 mA cm−2 at 0.66 V versus RHE), while c-NiO NSs tends to catalyze ORRs through 4-electron pathways to generate H2O. Theoretical calculations indicate that the changed short-range order of a-NiO NSs leads to alteration of Ni d-orbital states, which can regulate the adsorption orientation and strength of ∗OOH intermediates to achieve high selectivity and activity of 2-electron ORRs.