A newly-explored Pd-based nanocrystal for the pH-universal electrosynthesis of H2O2

For the generation of hydrogen peroxide (H2O2), a robust electrocatalyst with high activity, selectivity and stability under pH-universal conditions is a formidable challenge. Herein, Pd4Se nanoparticles (NPs) have been proposed as a highly active, selective and durable electrocatalyst for H2O2 production over a wide pH range for the first time. In particular, the Pd4Se NPs show superior H2O2 production selectivities of 93.5%, 89.7%, and 86.7% in 0.1 M HClO4, 0.1 M KCl and 0.1 M KOH electrolytes, respectively. Density functional theory (DFT) calculations reveal that Se incorporation prevents the OO early-cleavage issue by suppressing the excessive electronegativity of the Pd sites. In addition, a strong p-d repulsive correlation shifts the Pd-4d band towards the electron-depleting centre, allowing near-barrier-free electron transfer and facilitating OOH- stabilization. Owing to a high energy barrier of the dissociation of OOH-, the four-electrons oxygen reduction pathway is significantly suppressed for high H2O2 selectivity. The Pd4Se NPs are also highly stable, with only a 2.4%, 9.6% and 3.4% decrease for H2O2 selectivity in 0.1 M HClO4, 0.1 M KCl and 0.1 M KOH electrolytes, respectively, after 5000 cycles, which shows that these NPs are a unique and robust Pd-based electrocatalyst for H2O2 generation under pH-universal conditions.