Earth-Abundant Copper-Based Bifunctional Electrocatalyst for Both Catalytic Hydrogen Production and Water Oxidation

Copper(i) tertiary phosphine xanthate complexes as single source precursors for copper sulfide and their application in the OER

Three heteroleptic bis(triphenylphosphine)copper(i) methyl pyridyl xanthate complexes used as single source precursors for copper sulfide and the resulting copper sulfides have been utilized for the electrocatalytic oxygen evolution reaction.

Helical carbon tubes derived from epitaxial Cu-MOF coating on textile for enhanced supercapacitor performance

A new helical carbon tube material has been prepared from epitaxial Cu-MOF coating on textile by calcination treatment.

Fabrication of strong bifunctional electrocatalytically active hybrid Cu–Cu2O nanoparticles in a carbon matrix

Earth-abundant copper-based hybrid Cu–Cu₂ONPs@C in the carbon matrix exhibited enhanced OER and HER catalytic activity compared to pure Cu₂O and CuNPs@C.

Electronic Modulation of Electrocatalytically Active Center of Cu7S4 Nanodisks by Cobalt-Doping for Highly Efficient Oxygen Evolution Reaction

Cu-based electrocatalysts have seldom been studied for water oxidation because of their inferior activity and poor stability regardless of their low cost and environmentally benign nature. Therefore, exploring an efficient way to improve the activity of Cu-based electrocatalysts is very important for their practical application. Modifying electronic structure of the electrocatalytically active center of electrocatalysts by metal doping to favor the electron transfer between catalyst active sites and electrode is an important approach to optimize hydrogen and oxygen species adsorption energy, thus leading to the enhanced intrinsic electrocatalytic activity. Herein, Co-doped Cu₇S₄ nanodisks were synthesized and investigated as highly efficient electrocatalyst for oxygen evolution reaction (OER) due to the optimized electronic structure of the active center. Density-functional theory (DFT) calculations reveal that Co-engineered Cu₇S₄ could accelerate electron transfer between Co and Cu sites, thus decrease the energy barriers of intermediates and products during OER, which are crucial for enhanced catalytic properties. As expected, Co-engineered Cu₇S₄ nanodisks exhibit a low overpotential of 270 mV to achieve current density of 10 mA cm^-2 as well as decreased Tafel slope and enhanced turnover frequencies as compared to bare Cu₇S₄. This discovery not only provides low-cost and efficient Cu-based electrocatalyst by Co doping, but also exhibits an in-depth insight into the mechanism of the enhanced OER properties.

Stable and Efficient CuO Based Photocathode through Oxygen-Rich Composition and Au-Pd Nanostructure Incorporation for Solar-Hydrogen Production

Enhancing stability against photocorrosion and improving photocurrent response are the main challenges toward the development of cupric oxide (CuO) based photocathodes for solar-driven hydrogen production. In this paper, stable and efficient CuO-photocathodes have been developed using in situ materials engineering and through gold-palladium (Au-Pd) nanoparticles deposition on the CuO surface. The CuO photocathode exhibits a photocurrent generation of ∼3 mA/cm² at 0 V v/s RHE. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis and X-ray spectroscopy (XPS) confirm the formation of oxygen-rich (O-rich) CuO film which demonstrates a highly stable photocathode with retained photocurrent of ∼90% for 20 min. The influence of chemical composition on the photocathode performance and stability has been discussed in detail. In addition, O-rich CuO photocathodes deposited with Au-Pd nanostructures have shown enhanced photoelectrochemical performance. Linear scan voltammetry characteristic shows ∼25% enhancement in photocurrent after Au-Pd deposition and reaches ∼4 mA/cm² at "0" V v/s RHE. Hydrogen evolution rate significantly depends on the elemental composition of CuO and metal nanostructure. The present work has demonstrated a stable photocathode with high photocurrent for visible-light-driven water splitting and hydrogen production.

In-situ Electrodeposition of Highly Active Silver Catalyst on Carbon Fiber Papers as Binder Free Cathodes for Aluminum-air Battery

Carbon fiber papers supported Ag catalysts (Ag/CFP) with different coverage of electro-active site are prepared by electrochemical deposition and used as binder free cathodes in primary aluminum-air (Al-air) battery. Scanning Electron Microscopy and X-ray Diffraction studies are carried out to characterize the as-prepared Ag/CFP air cathodes. Oxygen reduction reaction (ORR) activities on these air cathodes in alkaline solutions are systematic studied. A newly designed aluminum-air cell is used to further determine the cathodes performance under real operation condition and during the test, the Ag/CFP electrodes show outstanding catalytic activity for ORR in concentrated alkaline electrolyte, and no obvious activity degradation is observed after long-time discharge. The electrochemical test results display the dependence of coverage of the electro-active Ag on the catalytic performance of the air cathodes. The resulting primary Al-air battery made from the best-performing cathode shows an impressive discharge peak power density, outperforming that of using commercial nano-manganese catalyst air electrodes.

Crystalline Copper Phosphide Nanosheets as an Efficient Janus Catalyst for Overall Water Splitting

Hydrogen is essential to many industrial processes and could play an important role as an ideal clean energy carrier for future energy supply. Herein, we report for the first time the growth of crystalline Cu₃P phosphide nanosheets on conductive nickel foam (Cu₃P@NF) for electrocatalytic and visible light-driven overall water splitting. Our results show that the Cu₃P@NF electrode can be used as an efficient Janus catalyst for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). For OER catalysis, a current density of 10 mA/cm² requires an overpotential of only ∼320 mV and the slope of the Tafel plot is as low as 54 mV/dec in 1.0 M KOH. For HER catalysis, the overpotential is only ∼105 mV to achieve a catalytic current density of 10 mA cm^-2. Moreover, overall water splitting can be achieved in a water electrolyzer based on the Cu₃P@NF electrode, which showed a catalytic current density of 10 mA/cm² under an applied voltage of ∼1.67 V. The same current density can also be obtained using a silicon solar cell under ∼1.70 V for both the HER and the OER. This new Janus Cu₃P@NF electrode is made of inexpensive and nonprecious metal-based materials, which opens new possibilities based on copper to exploit overall water splitting for hydrogen production. To the best of our knowledge, such high performance of a copper-based water oxidation and overall water splitting catalyst has not been reported to date.

Electrocatalytic water oxidation by Cu(ii) ions in a neutral borate buffer solution

Herein we report that a Cu(ii) salt can efficiently catalyze water oxidation in a neutral borate buffer.

A new preparation of a bifunctional crystalline heterogeneous copper electrocatalyst by electrodeposition using a Robson-type macrocyclic dinuclear copper complex for efficient hydrogen and oxygen evolution from water

Electro-deposited Cu(OH)₂/Cu₂O-based thin film on FTO with the macrocyclic dicopper complex shows excellent water splitting activity in excellent Faradaic efficiency.

A bimetallic carbide derived from a MOF precursor for increasing electrocatalytic oxygen evolution activity

Through different thermal treatments, an obvious phase transformation has been observed in a microporous bimetallic metal–organic framework InOF-16, from binary In₂O₃ and Co₃O₄ in oxygen to binary In₂O₃ and Co₃InC_0.75 in argon.

The mechanism change by switching the reactants from water to hydroxyl ions for electrocatalytic water oxidation: a case study of copper oxide microspheres

The as-obtained CuO microspheres can serve as an active and stable water oxidation catalyst under electrochemical reaction conditions and operate at modest overpotential providing an alternative to the Co-WOC catalyst for applications in solar energy storage.

A Highly Active and Robust Copper-Based Electrocatalyst toward Hydrogen Evolution Reaction with Low Overpotential in Neutral Solution

Although significant progress has been made recently, copper-based materials have long been considered to be ineffective catalysts toward the hydrogen evolution reaction (HER), in most cases, requiring high overpotentials more than 300 mV. We report here that a Cu(0)-based nanoparticle film electrodeposited in situ from a Cu(II) oxime complex can act as a highly active and robust HER electrocatalyst in neutral phosphate buffer solution. The as-prepared nanoparticle film is of poor crystallization, which incorporates significant amounts of oxime ligand residues and buffer anions PO₄^3-. The proposed mechanism suggests that the Cu(0)-based nanoparticle film is activated with incorporated or adsorbed PO₄^3- anions and the PO₄^3- anions-anchored sites might serve as the actual catalytic active sites with efficient proton transport mediators. Catalysis occurs with a low onset overpotential (η) of 65 mV, and a current density of 1 mA/cm² can be achieved with η = 120 mV. The nanoparticle film shows an excellent catalytic durability with slightly rising current density during electrolysis, presumably due to further incorporation or adsorption of PO₄^3- anions in the process. This electrocatalyst not only forms in situ from earth-abundant materials but also operates in neutral water with low overpotential and high stability.

Ultra-high electrochemical catalytic activity of MXenes

Cheap and abundant electrocatalysts for hydrogen evolution reactions (HER) have been widely pursued for their practical application in hydrogen-energy technologies. In this work, I present systematical study of the hydrogen evolution reactions on MXenes (Mo₂X and W₂X, X = C and N) based on density-functional-theory calculations. I find that their HER performances strongly depend on the composition, hydrogen adsorption configurations, and surface functionalization. I show that W₂C monolayer has the best HER activity with near-zero overpotential at high hydrogen density among all of considered pure MXenes, and hydrogenation can efficiently enhance its catalytic performance in a wide range of hydrogen density further, while oxidization makes its activity reduced significantly. I further show that near-zero overpotential for HER on Mo₂X monolayers can be achieved by oxygen functionalization. My calculations predict that surface treatment, such as hydrogenation and oxidization, is critical to enhance the catalytic performance of MXenes. I expect that MXenes with HER activity comparable to Pt in a wide range of hydrogen density can be realized by tuning composition and functionalizing, and promotes their applications into hydrogen-energy technologies.

A Copper Porphyrin-Based Conjugated Mesoporous Polymer-Derived Bifunctional Electrocatalyst for Hydrogen and Oxygen Evolution

Scalable and robust catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are required for the implementation of water splitting technologies as a globally applicable method of producing renewable hydrogen. Herein, we report nitrogen-enriched porous carbon materials containing copper/copper oxide, derived from copper porphyrin-based conjugated mesoporous polymers (CMPs), as a bifunctional catalyst for both HER and OER. These catalysts have a high surface area, unique tubular structure, and strong synergistic effect of copper/copper oxide and porous carbons, resulting in excellent performance for water splitting. Under optimal conditions, the catalyst exhibits a quite low overpotential for OER (350 mV to reach 1.0 mA cm(-2) and 450 mV to reach 10 mA cm(-2) ) in alkaline media, which places it among the best copper-based water oxidation catalysts reported in the literature. Furthermore, the catalyst shows good catalytic activity for HER at a low overpotential (190 mV to reach 1.0 mA cm(-2) ) as well as a high current density (470 mV to reach 50 mA cm(-2) ). The results suggest that hybridized copper/carbon materials are attractive noble-metal-free catalysts for water splitting.

Self-Supported Cedarlike Semimetallic Cu3P Nanoarrays as a 3D High-Performance Janus Electrode for Both Oxygen and Hydrogen Evolution under Basic Conditions

There has been strong and growing interest in the development of cost-effective and highly active oxygen evolution reaction (OER) electrocatalysts for alternative fuels utilization and conversion devices. We report herein that semimetallic Cu3P nanoarrays directly grown on 3D copper foam (CF) substrate can function as effective electrocatalysts for water oxidation. Specifically, the surface oxidation-activated Cu3P only required a relatively low overpotential of 412 mV to achieve a current density of 50 mA cm(-2) and displayed a small Tafel slope of 63 mV dec(-1) in 0.1 M KOH solution, on account of the collaborative effect of large roughness factor (RF) and semimetallic character. Following that, investigations into the mechanism revealed the formation of a unique active phase during the water oxidation process in which conductive Cu3P was the core covered with a thin copper oxide/hydroxide layer. Moreover, this Cu3P 3D electrode was also applied to the hydrogen evolution reaction (HER) and showed good catalytic performance and stability under the same basic conditions.

Self-Supported Cu-Based Nanowire Arrays as Noble-Metal-Free Electrocatalysts for Oxygen Evolution

Crystalline Cu-based nanowire arrays (NWAs) including Cu(OH)2 , CuO, Cu2 O, and CuOx are facilely grown on Cu foil and are found to act as highly efficient, low-cost, and robust electrocatalysts for the oxygen evolution reaction (OER). Impressively, this noble-metal-free 3 D Cu(OH)2 -NWAs/Cu foil electrode shows the highest catalytic activity with a Tafel slope of 86 mV dec(-1) , an overpotential (η) of about 530 mV at ∼10 mA cm(-2) (controlled-potential electrolysis method without iR correction) and almost 100 % Faradic efficiency, paralleling the performance of the state-of-the-art RuO2 OER catalyst in 0.1 m NaOH solution (pH 12.8). To the best of our knowledge, this work represents one of the best results ever reported on Cu-based OER systems.

Fuzzy, copper-based multi-functional composite particles serving simultaneous catalytic and signal-enhancing roles

Multifunctional plasmonic particles serving simultaneously as catalysts and label-free reporting agents are highly pursued due to their great potential in enhancing reaction operational efficiencies. Copper is an abundant and economic resource, and it possesses practical applicability in industries, but no dual-functional copper-based catalytic and self-reporting particles have been reported so far. This study proposes a facile strategy to prepare high-performance dual-functional copper-based composite particles that catalyze reactions and simultaneously serve as a SERS (surface enhanced Raman spectra) active, label-free reporting agent. Polyelectrolyte-modified reduced graphene oxide particles are used as the reactive precursors in the fabrication method. Upon adding Cu(NO3)2 solutions into the precursor dispersions, composite particles comprised by copper/copper oxide core and polyelectrolyte-graphene shell were facilely obtained under sonication. The as-prepared composite particles efficiently catalyzed the conversion of 4-nitrophenol to 4-aminophenol and simultaneously acted as the SERS-active substrate to give enhanced Raman spectra of the produced 4-aminophenol. Taking advantage of the assembling capabilities of polyelectrolyte shells, the composite particles could be further assembled onto a planar substrate to catalyze organic reactions, facilitating their application in various conditions. We expect this report to promote the fabrication and application of copper-based multifunctional particles.

Self-supported nanoporous NiCo2O4 nanowires with cobalt-nickel layered oxide nanosheets for overall water splitting

Water splitting via the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in producing H2 and O2 is a very important process in the energy field. Developing an efficient catalyst which can be applied to both HER and OER is crucial. Here, a bifunctional catalyst, CFP/NiCo2O4/Co0.57Ni0.43LMOs, has been successfully fabricated. It exhibits remarkable performance for OER in 0.1 M KOH producing a current density of 10 mA cm(-2) at an overpotential of 0.34 V (1.57 V vs. RHE), better than that of the commercial Ir/C (20%) catalyst. Simultaneously, it also exhibits good catalytic performance for HER in 0.5 M H2SO4 producing a current density of 10 mA cm(-2) at an overpotential of 52 mV and a Tafel slope of 34 mV dec(-1), approaching that of the commercial Pt/C (20%) nanocatalyst. Particularly, CFP/NiCo2O4/Co0.57Ni0.43LMOs present better durability under harsh OER and HER cycling conditions than commercial Ir/C and Pt/C. Furthermore, an H-type electrolyzer was fabricated by applying CFP/NiCo2O4/Co0.57Ni0.43LMOs as the cathode and anode electrocatalyst, which can be driven by a single-cell battery. This bifunctional catalyst will be very promising in overall water splitting.

In situ generated highly active copper oxide catalysts for the oxygen evolution reaction at low overpotential in alkaline solutions

A highly active copper oxide catalyst film is generated in situ from copper(ii) diamine complex for oxygen evolution reaction with high performance and excellent durability in alkaline solutions.

New insights into water oxidation reactions from photocatalysis, electrocatalysis to chemical catalysis: an example of iron-based oxides doped with foreign elements

Our study provides the first critical evaluation of the three common driving forces. The data clearly demonstrate that water oxidation catalytic performance can differ widely and depend strongly on the driving force employed.

Copper complexes as catalyst precursors in the electrochemical hydrogen evolution reaction

Two copper complexes were investigated with respect to their activity in the electrocatalysed hydrogen evolution reaction. The complexes are precursors for highly active copper(0) and Cu₂O deposits.

Pyrolyzed cobalt porphyrin-based conjugated mesoporous polymers as bifunctional catalysts for hydrogen production and oxygen evolution in water

A series of cobalt-porphyrin based conjugated mesoporous polymers were fabricated as catalyst precursors to generate bifunctional catalysts for both the OER and the HER.

Facile synthesis of porous CuO polyhedron from Cu-based metal organic framework (MOF-199) for electrocatalytic water oxidation

Metal–organic frameworks have been demonstrated as suitable metal sources and sacrificial templates for preparation of porous transition-metal oxide nanomaterials.

Fabrication of a Core-Shell-Type Photocatalyst via Photodeposition of Group IV and V Transition Metal Oxyhydroxides: An Effective Surface Modification Method for Overall Water Splitting

The design of optimal surface structures for photocatalysts is a key to efficient overall water splitting into H2 and O2. A unique surface modification method was devised for a photocatalyst to effectively promote overall water splitting. Photodeposition of amorphous oxyhydroxides of group IV and V transition metals (Ti, Nb, Ta) over a semiconductor photocatalyst from corresponding water-soluble metal peroxide complexes was examined. In this method, amorphous oxyhydroxide covered the whole surface of the photocatalyst particles, creating a core-shell structure. The water splitting behavior of the novel core-shell-type photocatalyst in relation to the permeation behavior of the coating layer was investigated in detail. Overall water splitting proceeded successfully after the photodeposition, owing to the prevention of the reverse reaction. The photodeposited oxyhydroxide layers were found to function as molecular sieves, selectively filtering reactant and product molecules. By exploiting the selective permeability of the coating layer, redox reactions on the photocatalyst surface could be suitably controlled, which resulted in successful overall water splitting.

Robust and highly active copper-based electrocatalyst for hydrogen production at low overpotential in neutral water

A Cu(0)-based catalyst free of noble metals was used as an electrocatalyst in the hydrogen evolution reaction in neutral water with an onset overpotential of only 70 mV.

Efficient visible light-driven water oxidation catalyzed by an all-inorganic copper-containing polyoxometalate

We report the first copper-containing POM catalyst [Cu₅(OH)₄(H₂O)₂(A-α-SiW₉O₃₃)₂]¹⁰⁻(1) that catalyzes water oxidation under visible light. Multiple experiments confirm that1is an active and dominant catalyst during water oxidation.