Optimization of Oxygen Evolution Reaction with Electroless Deposited Ni–P Catalytic Nanocoating

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.

Facile Synthesis of Sulfate-Intercalated CoFe LDH Nanosheets Derived from Two-Dimensional ZIF-9(III) for Promoted Oxygen Evolution Reaction

“…Indeed, the turnover frequency (TOF) is an important parameter for catalysts. Generally, there are two approaches to determine the TOF, denoted by TOF total metal (TOF tm ) and TOF redox [44,45]. As displayed in Figure S7, the TOF change trends for CoFe LDH and ZIF-9(III) catalysts are positively correlated with overpotential.…”

Enhanced electrocatalytic activity of low-cost NiO microflowers on graphene paper for the oxygen evolution reaction

“…To better investigate the metrics related to the intrinsic activity of the electrodes, the turnover frequency (TOF) must be considered. 17,48 The TOF is dened as the rate of production of oxygen molecules per active site:…”

“…where I is the measured current at a xed overpotential, the term 4 represents the number of electrons involved in the OER, F is the Faraday constant and n is the number of moles of the active sites 48 (see the ESI † for details of the calculation of TOF). The greatest difficulties arise when determining the number of active sites.…”

“…It is possible to use the rst backward sweep of a CV scan and integrate the charge under the reduction peak. 48 The n for TOF redox can be calculated by the following expression:…”

“…This discrepancy arises from the consideration that not all the catalyst mass deposited on GP is electrochemically active during the OER, but only a small fraction of the total mass contributes active sites to the reaction. 47,48 To evaluate and compare the intrinsic catalytic activity, it is important to look at the activity per unit mass (A mg À1 , see the ESI † for details). 3b compares the mass activity of the NiO catalysts at a current density of 10 mA cm À2 by considering both the total loading of mFs and only the redox contribution to the OER.…”