Realizing the Synergy of Interface Engineering and Chemical Substitution for Ni3N Enables its Bifunctionality Toward Hydrazine Oxidation Assisted Energy‐Saving Hydrogen Production

Abstract Hydrazine oxidation assisted water electrolysis offers a unique rationale for energy‐saving hydrogen production, yet the lack of effective non‐noble‐metal bifunctional catalysts is still a grand challenge at the current stage. Here, the Mo doped Ni 3 N and Ni heterostructure porous nanosheets grow on Ni foam (denoted as MoNi 3 N/Ni/NF) are successfully constructed, featuring simultaneous interface engineering and chemical substitution, which endow the outstanding bifunctional electrocatalytic performances toward both hydrazine oxidation reaction (HzOR) and hydrogen evolution reaction (HER), demanding a working potential of −0.3 mV to reach 10 mA cm −2 for HzOR and −45 mV for that of HER. Impressively, the overall hydrazine splitting (OHzS) system requires an ultralow cell voltage of 55 mV to deliver 10 mA cm −2 with remarkable long‐term durability. Moreover, as a proof‐of‐concept, economical H 2 production systems utilizing OHzS unit powered by a waste AAA battery, a commercial solar cell, and a homemade direct hydrazine fuel cell (DHzFC) are investigated to inspire future practical applications. The density functional theory calculations demonstrate that the synergy of Mo substitution and abundant Ni 3 N/Ni interface owns a more thermoneutral value for H* absorption ability toward HER and optimized dehydrogenation process for HzOR.