Resolving the Mass Transfer Conflict via Spatially Differentiated Hydrogen Bond Network Modulation for Hydrazine Oxidation

Abstract Replacing the sluggish oxygen evolution reaction with thermodynamically favorable small-molecule oxidation reactions enables energy-efficient hydrogen production, yet alkaline systems face an inherent conflict because neutral substrates and OH− impose incompatible demands on the interfacial hydrogen bond network. Neutral molecules require a loose network for diffusion, whereas OH− transport via the Grotthuss mechanism strictly depends on a continuous one, creating a mass transfer bottleneck that has been largely overlooked. Here, we use the hydrazine oxidation reaction (HzOR) as a model and resolve this conflict through spatially differentiated dual modulation of the interfacial hydrogen bond network via a multiscale electric field on fluorine-doped cobalt phosphide (F-CoP). The interfacial electric fields enhanced by a positive shift in the potential of zero charge drive K+ accumulation to disrupt midrange hydrogen bonds for fast N2H4 diffusion, while atomic-scale local fields at F sites anchor water molecules via hydrogen bonds to restore short-range network connectivity for efficient OH− transport. This spatially distinct mechanism enables the F‑CoP electrocatalyst to require only 0.293 V at 100 mA/cm2 for hydrazine-assisted water splitting, 1.53 V lower than conventional water splitting. This work establishes spatially resolved interfacial hydrogen bond modulation as a general framework for resolving bimolecular mass transfer conflicts in alkaline electrocatalysis.