Investigation of the Kinetics and Mass Transport Aspects of Hydrogen Evolution during Electroless Deposition of Nickel–Phosphorus

Abstract

Electroless deposition of nickel-phosphorus (Ni-P) alloy, facilitated by the use of sodium hypophosphite as reducing agent, is important to many industrial applications. During electroless Ni-P deposition, hydrogen gas evolves as a by-product. In this paper, we first analyze the source of hydrogen evolution. Specifically, we demonstrate that hydrogen gas evolves primarily due to chemical hydroxylation of hypophosphite anions catalyzed by the Ni surface and not due to electrochemical water splitting. Then, using careful volumetric measurements of the rate of hydrogen evolution on a rotating disc electrode, the effects of pH, hypophosphite concentration and hydrodynamics on the hypophosphite hydroxylation reaction are investigated. A mathematical rate expression is formulated, which incorporates the relevant kinetic and mass transport parameters affecting the hypophosphite hydroxylation reaction. Comparison of the model with experimental hydrogen evolution rate measurements allows precise determination of the rate constant and reaction orders. The approach presented herein has broad applicability to the study of gas evolution kinetics in chemical systems where access to the reaction rate is not available through amperommetry.

Electroless Metallization of the Elements: Survey and Progress

“…668−678 Therefore, in the interests of brevity and clarity, we present only the description offered by Yin et al 678,679 as a representative example for acidic EL NiP baths, where P codeposition is favored. 680 Similar mechanisms have been proposed in alkaline solution, based on results from kinetics studies 681,682…”

“…The half reaction describing P deposition is normalH 2 PO 2 − + 2 normalH + + normale − → normalP 0 postfixfalse↓ infix+ 2 normalH 2 normalO Although significant research has been done to ascertain the P deposition mechanism, differing mechanisms are consistent with experimental rates laws obtained for EL NiP deposition. − Therefore, in the interests of brevity and clarity, we present only the description offered by Yin et al , as a representative example for acidic EL NiP baths, where P codeposition is favored . Similar mechanisms have been proposed in alkaline solution, based on results from kinetics studies , and a β-Ni(OH) ads oxide adsorbate layer on the Ni surface as a catalyst for HPO 2 – adsorbate oxidation. , …”

YSZ/Ni double‐shell powder via surface electroless deposition tuned by an active kinetic model

“…In the initial stage of EN plating, Pd activation centers were distributed the surface of the ceramic layer first, and catalytic centers grew from nickel nuclei into nickel particles and then gradually grew to form a continuous nickel layer 42 . After Pd on the ceramic surface catalyzes the deposition of nickel, under the reduction of hypophosphite, the nickel particles undergo an autocatalytic deposition reaction on the ceramic surface 43,44 . And with H 2 PO$$_2^ - $$as a reducing agent in the plating solution, the reaction equation is 29 : $$$$\begin{equation}{\rm{Ni}}^{2 + } + {{\rm{H}}}_2{\rm{PO}} + {{\rm{H}}}_2{\rm{O}} \to {\rm{HPO}}_3^{2 - } + {\rm{Ni}} + {{\rm{H}}}^ + + {{\rm{H}}}_2\end{equation}$$$$ $$$$\begin{equation}{{\rm{H}}}_2{\rm{PO}} + 2{{\rm{H}}}^ + \to {\rm{P}} + 2{{\rm{H}}}_2{\rm{O}}.\end{equation}$$$$…”

“…42 After Pd on the ceramic surface catalyzes the deposition of nickel, under the reduction of hypophosphite, the nickel particles undergo an autocatalytic deposition reaction on the ceramic surface. 43,44 And with H 2 PO − 2 as a reducing agent in the plating solution, the reaction equation is 29 :…”

Synthesis of Dilute Phosphorous-Embedded Co Alloy Films on a NiSi Substrate with a Superior Gap-Filling Capability for Nanoscale Interconnects

“…Additionally, hydrogen evolution can also be triggered by a chemical hydroxylation of hypophosphite anions that is catalyzed by Ni, instead of the electrolysis of water mentioned above; therefore electroless deposition through the following reaction can occur. 39 [ ]…”