Accelerating hydrazine-assisted hydrogen production kinetics with Mn dopant modulated CoS2 nanowire arrays

Abstract

Electrochemical H₂ production from water splitting is an environmentally sustainable technique but remains a great challenge due to the sluggish anodic oxygen evolution reaction (OER). Replacing the OER with the thermodynamically more favorable electrocatalytic oxidation process is an effective strategy for highly efficient H₂ generation. Herein, Mn-doped CoS₂ has predicted an excellent bifunctional electrocatalyst for the hydrogen evolution reaction (HER) and the hydrazine oxidation reaction (HzOR). With the introduction of Mn, the Gibbs free energy of the adsorbed H* and the potential rate-limiting step (the dehydrogenation of *NH₂NH₂ to *NHNH₂) for the HzOR process of the catalyst can be significantly reduced. As expected, the Mn-CoS₂ catalyst exhibited excellent catalytic activity and robust long-term stability for the HER and HzOR. In detail, the Mn-CoS₂ catalyst only acquired potentials of 46 and 77 mV versus the reversible hydrogen electrode for achieving a current density of 10 mA cm⁻² for the cathodic HER and anodic HzOR, respectively. In addition, the Mn-CoS₂ electrode only needs a cell voltage of 447 mV to output 200 mA cm⁻² in the overall hydrazine splitting system as well as exhibits a robust long-term H₂ production. This work provides theoretical guidance for the design of advanced bifunctional electrocatalysts and promotes high efficiency and energy-saving H₂ production technology.