High-capacitance AC-NiMo LDH composite electrode as redox mediator for efficient decoupled water electrolysis

Abstract

Layered double hydroxides (LDHs), serving as an efficient redox mediator, has exhibit distinct advantages in the decoupled electrolytic water splitting hydrogen production system. However, its intrinsic low conductivity poses a significant challenge to its broader application. Here, a composite AC-NiMo LDH redox mediator (RM) was synthesized using activated carbon as the growth substrate through a hydrothermal synthesis method involving water. Electrochemical testing shows that the AC-NM LDH10 has excellent performance with a specific capacitance of 676.3 F g⁻¹ at a current density of 1 A g⁻¹ (is 2.28 times that of NiMo LDH). In addition, this composite RM electrode exhibited a high buffering capacity for 400 s under 2 mA cm⁻² during the decoupled H₂/O₂ evolution. In the conventional coupled system, the necessary input voltage of 1.53 V was separated into two lower ones, 1.44/0.29 V for H₂/O₂ evolutions in the decoupled system, respectively. Furthermore, after 60 cycles of testing, there was almost no change in its cell voltage. This architecture reduces total energy consumption relative to conventional coupled systems, establishing a technologically viable pathway for safe, high-efficiency hydrogen production