Self‐Supported Electrocatalysts Derived from Nickel‐Cobalt Modified Polyaniline Polymer for H₂‐Evolution and O₂‐Evolution Reactions

Abstract

The water splitting aims to produce H 2 for fuel cells and a number of industrial processes such as the ammonia synthesis and the metals refining. There is actually a major limitation about the development of cost-effective and efficient electrocatalysts to lower the cell voltage that must be overcome to perform sequentially the overall reaction that is 2H 2 O !2H 2 + O 2. In the present study, we combined Ni and Co as the promising alternative catalytic metals to Pt-group metals as well as N and S as the doping elements to fabricate self-supported electrocatalysts for hydrogen evolution (HER) and oxygen evolution (OER) in alkaline media. To these ends, the polymerization of the aniline into polyaniline (PANI) in the presence of Ni(II) and Co(II) followed by calcination in air resulted in the formation of heterogeneous catalytic materials self-supported onto a matrix made of C, N, S, Ni and Co. Enhanced activity and durability were recorded for the hybrid and bimetallic PANI-NiCo composite.

Iridium and Ruthenium Modified Polyaniline Polymer Leads to Nanostructured Electrocatalysts with High Performance Regarding Water Splitting

“…The pristine polymer-based materials were synthesized via the chemical oxidative polymerization of aniline into polyaniline (PANI) in hydrochloric acid by ammonium persulfate. We previously showed that using ammonium persulfate as the oxidizing agent produces an emeraldine form of PANI (with polaron/bipolaron amount of 43% and base amount of 54% [ 21 ]) by using a set of physicochemical and electrochemical screenings [ 2 , 3 , 21 ]. So, the present work focuses on the polymer modified by iridium and ruthenium ( Figure 1 a) in an attempt to produce hybrid nanostructured materials with high-performance regarding HER and OER after a calcination step.…”

“…The different materials were synthesized by modifying our initial method [ 2 , 3 ]. Typically, 25 mL solution made of 0.5 M HCl and 0.4 M ANI was first prepared and put into a reactor at 5 °C.…”

“…Chung et al [ 1 ] have shown that an electrode’s electrical resistance (thus its conductivity) strongly affects the metrics of electrochemical activity and this becomes a concern for high mass loadings (increased thicknesses), before concluding that the electrical conductivity should be considered as one of the essential criteria when designing active materials for real electrochemical energy storage/conversion applications. The interest towards conducting polymer (nano)structures is growing yearly in (bio)electrochemistry as either precursors of freestanding electrocatalysts [ 2 , 3 ] or a supports [ 4 , 5 , 6 ] for active sites based on enzyme/abiotic catalysts. For both purposes, recent studies show that the combination of polyaniline (a conducting polymer) and metallic species (Ni, Co, Mo) produces nanostructured materials with high performance regarding the electrocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and water splitting [ 2 , 3 , 7 , 8 ].…”

“…In heterogeneous electrocatalysis of water splitting, however, metal oxides (MO 2 , M = Ir, Ru) or oxy-hydroxides (MO(OH), M = Ni, Fe, Co, etc.) are the state-of-the-art for OERs [ 9 , 10 , 11 ], while metals (Rh, Pt, Ir) are suitable for HERs [ 12 , 13 ] (also non-noble [ 2 , 14 , 15 , 16 ]), regulated by the oxophilicity character of the surfaces [ 17 , 18 ]. Basically, those metal nanoparticles are initially prepared before the used of carbon black to lower the metal content, which does not enable the maximization of the electrocatalytic performance and minimization of the loss of active sites during the long-term operation.…”

Insights on the Electrocatalytic Seawater Splitting at Heterogeneous Nickel-Cobalt Based Electrocatalysts Engineered from Oxidative Aniline Polymerization and Calcination

“…We have utilized the oxidative aniline polymerization method by modifying our early process [ 41 , 42 , 43 ]. A solution S1 of 100 mL composed of 0.5 M HCl and 0.4 M ANI was prepared and kept at a controlled temperature of 5 °C.…”