Abstract
The low efficiency of water electrolysis mostly arises from the thermodynamic uphill oxygen evolution reaction. The efficiency can be greatly improved by rationally designing low-cost and efficient oxygen evolution anode materials. Herein, we report the synthesis of Ni–P alloys adopting a facile electroless plating method under mild conditions on nickel substrates. The relationship between the Ni–P properties and catalytic activity allowed us to define the best conditions for the electroless synthesis of highperformance Ni–P catalysts. Indeed, the electrochemical investigations indicated an increased catalytic response by reducing the thickness and Ni/P ratio in the alloy. Furthermore, the Ni–P catalysts with optimized size and composition deposited on Ni foam exposed more active sites for the oxygen evolution reaction, yielding a current density of 10 mA cm−2 at an overpotential as low as 335 mV, exhibiting charge transfer resistances of only a few ohms and a remarkable turnover frequency (TOF) value of 0.62 s−1 at 350 mV. The present study provides an advancement in the control of the electroless synthetic approach for the design and large-scale application of high-performance metal phosphide catalysts for electrochemical water splitting.
Highlights
Electrochemical water splitting has aroused unremitting attention as a promising method to produce H2, a clean and sustainable energy carrier considered an alternative to fossil fuels [1,2,3]
The electroless Ni–P alloys were synthesized in a solution containing 25 g L−1 nickel sulfate hexahydrate, which serves as the nickel source, 20 g L−1 sodium citrate as a complexing agent and 30 g L−1 ammonium fluoride as a stabilizer
Ni is reduced by capturing the electrons provided by the reducing chemical reaction can be described as follows [33]: agent (NaH2 PO2 ), while zero-valence P and H2 are formed as by-products
Summary
Electrochemical water splitting has aroused unremitting attention as a promising method to produce H2 , a clean and sustainable energy carrier considered an alternative to fossil fuels [1,2,3]. Electrolytic water generation is a thermodynamically uphill process, since the two semi-reactions involved, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), are constrained by sluggish kinetics, the OER, which undergoes a complex four-electron transfer process [4,5]. The large-scale application of these materials is hampered by their low abundance and high cost [7,8,9]. It is mandatory to seek earth-abundant and efficient OER electrocatalysts [10]. In this context, transition metalbased catalysts are undoubtedly compelling candidates in view of their abundancy, cost effectiveness and great potential in the field of OER for electrolytic water splitting [11,12]
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