Nitrogen and oxygen tailoring of a solid carbon active site for two-electron selectivity electrocatalysis

Abstract

The synthesis of hydrogen peroxide (H₂O₂) via two-electron (2e⁻) oxygen reduction reaction (ORR) electrocatalysis has garnered extensive attention as an appealing green and safe production technology. However, the key progress is still strongly dependent on developing highly active, selective and stable electrocatalysts. Here, guided by first-principles calculations, we developed a rational design for nitrogen (N) and oxygen (O) tailoring of carbon materials by precisely controlling the pyridinic N (Pydn-N) structure and the oxygen doping. The second nearest C atoms of Pydn-N were identified to be the active site, and this is suppressed owing to its local chemical environment and increase in the oxygen dopant content. Experimentally, high-temperature hydrogenation (HTH) regulates the Pydn-N content and synchronous oxygen removal for N,O co-doped carbons (CNO-x). The increment of Pydn-N from 37.42% up to 39.73%, along with oxygen removal from 5.24 at% down to 3.80 at% after HTH, promotes the H₂O₂ selectivity and electron transfer number (n) to 82% and 2.36. The H₂O₂ production rate is stable at around 200 mmol g_cat⁻¹ h⁻¹ and a faradaic efficiency (F.E.) of up to 80% was recorded during the initial 4 h. The long-term H₂O₂ production further highlights the significance of sustaining the Pydn-N structure, modulating the solid carbon active site.