In Situ Formation of Nanostructured Core–Shell Cu₃N–CuO to Promote Alkaline Water Electrolysis

Abstract

Electrochemical splitting of water to oxygen and hydrogen using earth-abundant first-row transition metal-based catalysts is a promising approach for sustainable energy conversion. Herein, we present a new convenient synthesis of copper nitride (Cu 3 N) that acts as a bifunctional electro(pre)catalyst for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water electrolysis in alkaline media. Strikingly, the electrophoretically deposited Cu 3 N on nickel foam (NF) displayed extremely low overpotentials for both OER and HER, and the overall water splitting cell potential was merely 1.62 V with a remarkable durability of over 10 days. Most notably, the coordinatively unsaturated Cu in Cu 3 N transformed in situ under a reducing environment and in an oxidative environment into a copper-rich shell that serves as the active site over an equally important electrically conductive Cu 3 N core to drive proficient catalysis. To the best of our knowledge, this is the first report on copper nitride for efficient and durable alkaline water electrolysis.

Stannites – A New Promising Class of Durable Electrocatalysts for Efficient Water Oxidation

“…The Cu 2p 3/2 and Cu 2p 1/2 spectrum exhibits sharp peaks at the binding energy of 931.9 and 951.7 eV, indicating the presence of a Cu I species . Additionally, satellite peaks typical for Cu II are located at the binding energies of 939.9, 942.6 and 961.2 eV . The low intensity of these satellites is in agreement with the deconvolution of the Cu 2p 3/2 and Cu 2p 1/2 peaks, revealing that most of the Cu is in the Cu I state with a minor contribution of Cu II .…”

“…[69] Additionally, satellite peaks typical for Cu II are located at the binding energies of 939.9, 942.6 and 961.2 eV. [14,69] The low intensity of these satellites is in agreement with the deconvolution of the Cu 2p 3/2 and Cu 2p 1/2 peaks, revealing that most of the Cu is in the Cu I state with a minor contribution of Cu II . The presence of mainly Cu I species strongly supports the hypothesis that iron is the actual active site and that the role of copper is likely another one such as facilitating electron transport.…”

“…Therefore, many of the oxides and most of the non‐oxidic materials are merely precatalysts for the OER . Even though the anion is often exchanged or depleted from the electrocatalytic active structure, it plays a significant role in tuning the properties of the active catalyst either by creating high surface areas and defects through leaching or by providing a conductive core …”

“…[11] Even though the anion is often exchanged or depleted from the electrocatalytic active structure, it plays a significant role in tuning the properties of the active catalyst either by creating high surface areas and defects through leaching or by providing a conductive core. [10][11][12][13][14][15] Bi-and multi-nuclear-TM (pre)catalysts have proven to be superior to mononuclear ones, as the variation of the metal composition enables the tuning of the intrinsic properties affecting the OER. [16,17] In this regard, it has been shown that an multinuclear assembling of metals helps to vary adsorption energies [2,18] and can afford higher stabilities, [19][20][21] conductivities [22][23][24] and surface areas [25,26] of OER catalysts.…”

Nitrogen Engineering on 3D Dandelion‐Flower‐Like CoS2 for High‐Performance Overall Water Splitting

“…Nevertheless, their widespread applications are severely limited by their high cost and scarcity. To this end, tremendous efforts have been devoted to develop highly efficient and cost‐effective electrocatalysts, such as transition metal oxides, selenides, borides, phosphides, nitrides, carbides, and sulfides . However, catalysts both used for OER and HER in the same electrolyte for water electrolysis taking the advantages of both simplifying the system and reducing the cost, usually suffer from low stability and inferior performance, which greatly impede their practical applications as bifunctional electrocatalysts.…”