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Cation-tunable flower-like (NiₓFe₁₋ₓ)₂P@graphitized carbon films as ultra-stable electrocatalysts for overall water splitting in alkaline media

Author:
Zhao, Hongyang, Wang, Yanwei, Fang, Ling, Fu, Weiwei, Yang, Xiaohui, You, Shili, Luo, Ping, Zhang, Huijuan, Wang, Yu
Source:
Journal of materials chemistry A 2019 v.7 no.35 pp. 20357-20368
ISSN:
2050-7496
Subject:
active sites, adsorption, anodes, carbon, catalysts, catalytic activity, cathodes, cost effectiveness, electric power, electrochemistry, electrolysis, encapsulation, energy, hydrogen, iron, nanoparticles, nickel, platinum, renewable energy sources, synergism
Abstract:
Electrocatalytic water splitting is a promising strategy for green and renewable energy development by transforming electrical energy into hydrogen energy. Herein, we report a series of flower-like electrocatalysts with cation-tunable (NiₓFe₁₋ₓ)₂P nanoparticles encapsulated by porous graphitized carbon films (GCs) via the combination of morphology control and component adjustment. By progressively tailoring the atomic ratios of Ni/Fe, the electronic structure and electrocatalytic activities of (NiₓFe₁₋ₓ)₂P can be intriguingly modified to achieve versatile catalytic behavior for both the HER and the OER. DFT calculations also validate that the (NiₓFe₁₋ₓ)₂P with an optimal atomic ratio of Ni/Fe can support the |ΔGH*| to be close to the optimum and decrease the adsorption energy for water, which can boost the water splitting. Meanwhile, anchoring the adjustable (NiₓFe₁₋ₓ)₂P nanoparticles into GC interlayers can endow these composites with more available active sites, excellent conductivity and enhanced stability. In fact, the combined synergistic effect of cation-tuned (NiₓFe₁₋ₓ)₂P nanoparticles and porous conductive GCs is the reason that these composites exhibit enhanced electrocatalytic activities, as illustrated by a low overpotential of 206 mV at j = 10 mA cm⁻² (256 mV at j = 50 mA cm⁻²) for the OER. Meanwhile, the bifunctional (Ni₀.₇₅Fe₀.₂₅)₂P@GCs, as both the cathode and anode of an electrolyzer, effectuates an ultra-small cell potential of 1.541 V at j = 10 mA cm⁻² (1.573 V at j = 20 mA cm⁻²) for 30 h during electrolysis of water, rivaling commercial IrO₂ and Pt/C catalysts. More importantly, this work can provide a way of fabricating cost-saving, component-tunable and high-efficiency bimetallic electrocatalysts for water splitting.
Agid:
6651413