No abstract

Given the abundant reserves of seawater and the scarcity of freshwater, real seawater electrolysis is a more economically appealing technology for hydrogen production relative to orthodox freshwater electrolysis. However, this technology is greatly precluded by the undesirable chlorine oxidation reaction and severe chloride corrosion at the anode, further restricting the catalytic efficiency of overall seawater splitting. Herein, a feasible strategy by engineering multifunctional collaborative catalytic interfaces is reported to develop porous metal nitride/phosphide heterostructure arrays anchoring on conductive Ni 2 P surfaces with affluent iron sites. Collaborative catalytic interfaces among iron phosphide, bimetallic nitride, and porous Ni 2 P supports play a positive role in improving water adsorption/dissociation and hydrogen adsorption behaviors of active Fe sites evidenced by theoretical calculations for hydrogen evolution reactions, and enhancing oxygenated species adsorption and nitrate-rich passivating layers resistant to chloride corrosion for oxygen evolution reaction, thus cooperatively propelling high-performance bifunctional seawater splitting. The resultant material Fe 2 P/Ni 1.5 Co 1.5 N/Ni 2 P performs excellently as a self-standing bifunctional catalyst for alkaline seawater splitting. It requires extremely low cell voltages of 1.624 and 1.742 V to afford current densities of 100 and 500 mA/cm 2 in 1 M KOH seawater electrolytes, respectively, along with superior long-term stability, outperforming nearly all the ever-reported non-noble bifunctional electrocatalysts and benchmark Pt/IrO 2 coupled electrodes for freshwater/seawater electrolysis. This work presents an effective strategy for greatly enhancing the catalytic efficiency of non-noble catalysts toward green hydrogen production from seawater electrolysis.

Alkaline water electrolysis is a commercially viable technology for green H 2 production using renewable electricity from intermittent solar or wind energy, but very few non-noble bifunctional catalysts simultaneously exhibit superb catalytic efficiency and stability at large current densities for hydrogen and oxygen evolution reactions (HER and OER, respectively), especially for ironbased catalysts. Given that iron is the most abundant and least expensive transition metal, iron-based compounds are very attractive low-cost targets as active electrocatalysts for bifunctional water splitting with large-current durability. Herein, the in situ construction of a self-supported Fe 2 P/Co 2 N porous heterostructure arrays possessing superb bifunctional catalytic activity in base is reported, featured by low overpotentials of 131 and 283 mV to attain a current density of 500 mA cm −2 for HER and OER, respectively, outperforming most of non-noble bifunctional electrocatalysts reported hitherto. Particularly, this hybrid catalyst also displays an excellent overall water splitting activity, requiring low voltages of 1.561 and 1.663 V to attain 100 and 500 mA cm −2 with excellent durability in 1 m KOH, respectively. Most importantly, the catalyst is stable for >120 h, even when the current density is 500 mA cm −2 , which is prominently superior to IrO 2 (+) //Pt (−) coupled noble electrodes, and is among the very best bifunctional catalysts reported thus far. Detailed theoretical calculations reveal that the interfacial interaction between Fe 2 P and Co 2 N can further improve the H* binding energy at the iron sites.

Seawater is the most abundant natural water resource in the world, which is an inexhaustible and low‐cost feedstock for hydrogen production by alkaline water electrolysis. It is appearling to develop robust and stable electrocatalysts for alkaline seawater electrolysis. However, the development of seawater electrolysis is seriously impeded by anodic chloride corrosion and chlorine evolution reaction, and few non‐noble electrocatalysts show prominent catalytic performance and excellent durability. Here, a heterogeneous electrocatalyst constructed by in situ growing highly dispersed iron‐rich bimetallic phosphide nanoparticles on metallic Ni3N (Fe2−2xCo2xP/Ni3N), which exhibits outstanding bifunctional catalytic activities for alkaline seawater splitting, is reported. The optimal (Fe0.74Co0.26)2P/Ni3N and Fe2P/Ni3N electrocatalysts demand only 113 and 212 mV to afford 100 mA cm−2 for hydrogen and oxygen evolution reactions (HER and OER) in 1 m KOH, respectively, thus substantially expediting overall water/seawater electrolysis at 100 mA cm−2 with 1.592/1.645 V. Particularly, Fe2P/Ni3N displays an unprecedented overpotential of 302 mV at 500 mA cm−2, which represents the best alkaline seawater oxygen evolution activity among the ever‐reported non‐noble electrocatalysts; and thus substantially expedites overall water/seawater splitting at 500 mA cm−2 with 1.701/1.768 V, surpassing most of the reported non‐noble lectrocatalysts. This work provides a new approach for developing high‐performance electrocatalysts for seawater splitting.