Electrochemical Investigation of the OER Activity for Nickel Phosphite-Based Compositions and Its Morphology-Dependent Fluorescence Properties

Abstract

Herein, we present the investigation of catalytical and fluorescence properties for Ni11(HPO3)8(OH)6 materials obtained through a hydrothermal approach. As part of the constant search for new materials that are both cost effective and electrocatalytically active for the oxygen evolution reaction (OER) in alkaline medium, the present study involves several graphite electrodes modified with Ni11(HPO3)8(OH)6 mixed with reduced graphene oxide (rGO) and carbon black. The experimental results obtained in 0.1 mol L–1 KOH electrolyte solution show the electrode modified with rGO, 5 mg carbon black and 1 mg nickel phosphite as displaying the highest current density. This performance can be attributed to the synergistic effect between nickel phosphite and the carbon materials. Investigation of the electrode’s OER performance in 0.1 mol L–1 KOH solution revealed a Tafel slope value of just 46 mV dec–1. By increasing the concentration to 0.5 and 1 mol L–1, this value increased as well, but there was a significant decrease in overpotential. Fluorescence properties were analyzed for the first time at the excitation length of 344 nm, and the observed strong and multiple emissions are described.

Advanced Electrocatalysts for the Oxygen Evolution Reaction: From Single- to Multielement Materials

“…Most earth-abundant materials that are OER-active are vulnerable to corrosion due to the acidic environment, while those that are acid-stable are inactive for the OER. Transition metals that have been identified as efficient OER catalysts include divalent cations of metals such as Mn, Fe, Co, and Ni, which exhibit electrocatalytic activity in the following order, Mn 2+ < Fe 2+ < Co 2+ < Ni 2+ [72]; this is due to a weakening of the metal-oxygen bond, resulting in reduced corrosion resistance [66]. Cations with high valence states are suggested as the active site for the OER, for example, Fe 3+ , Fe 4+ , Co 3+ , Co 4+ , or Mn 3+ , since the high oxidation states could serve as an electron acceptor [40].…”

Free-Base Porphyrin Aggregates Combined with Nickel Phosphite for Enhanced Alkaline Hydrogen Evolution

“…It evaluates the HER electrocatalytic properties in an alkaline medium of graphite electrodes modified with combinations between a transition metal-based compound-Ni 11 (HPO 3 ) 8 (OH) 6 -and each member from a series of four metalfree porphyrins. Previous reports have shown that nickel phosphite (NiPh) exhibits watersplitting catalytic activity [35][36][37][38]. As for the porphyrins, namely 5-(4-pyridyl)-10,15,20tris(4-phenoxyphenyl)porphyrin (P1), 5,10,15,20-tetrakis(4-allyloxyphenyl)porphyrin (P2), 5,10,15,20-tetrakis(p-tolyl)porphyrin (P3) and 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin (P4), they have been the focus of various studies reported by Fagadar et al [23,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53], during which they were thoroughly characterized by physical-chemical and electrochemical methods, and their potential applications were evidenced together with their HER and OER electrocatalytic activity in basic medium.…”