Enhancing acidic hydrogen evolution through pyrrolic nitrogen-doped reduced graphene oxide triggering two-electron oxygen reduction

Abstract

Developing cost-effective and efficient electrocatalysts is essential for addressing the slow kinetics and high overpotential in the hydrogen evolution reaction (HER), but significant challenges remain. Here, we fabricated the sandwich-structured HER electrodes using two types of N/O-doped graphene oxide films and Ni foam, denoted as Ni/N/O-rGO-1/Ni and Ni/N/O-rGO-2/Ni. Electrochemical analysis indicates that Ni/N/O-rGO-1/Ni presents superior HER performances in a 0.5 M H₂SO₄ solution at approximately 0 °C compared to Ni/N/O-rGO-2/Ni, such as an acceptable overpotential of 229 mV at 10 mA cm⁻², a Tafel slope of 162.0 mV dec⁻¹, and a 275 hour electrocatalytic lifespan with 17.82-fold current retention. After careful analysis, this attractive electrochemical stability can be attributed to the two-electron oxygen reduction (2e⁻-ORR) induced by pyrrolic nitrogen in N/O-rGO, which is confirmed by conducting HER tests on fresh Ni electrodes and investigating the impact of electrode spacing, solution temperature, and electrolyte types on the HER. To sum up, the discovery of the 2e⁻-ORR can improve the HER performance of Ni/N/O-rGO-1/Ni under harsh conditions, providing a feasible approach for developing efficient HER catalysts in demanding environments.