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Replacing the thermodynamically unfavorable oxygen evolution reaction (OER) with the low theoretical potential (−0.33 V) and safe by-product (N2/H2O) hydrazine oxidation reaction (HzOR) is an energy-saving way for hydrogen production. Nevertheless, the complexity of bifunctionality increases the difficulty of catalyst design. In this work, a hybrid of NiC2O4 and Nb2O5 is synthesized on nickel foam via a two-step low temperature reaction using Ni3S2 as a sacrificial template, named SNiC2O4–Nb2O5/NF. The experimental and theoretical calculation results illustrate that electrons are transferred from Ni to Nb, thus regulating the electronic structure of Ni. In the hybrid, Nb2O5 can effectively adsorb and split H2O, as well as downshift the d-band center of SNiC2O4, thereby optimizing the Volmer step. SNiC2O4–Nb2O5/NF achieves the properties for the hydrogen evolution reaction (HER: η20 = 155 mV) and the oxygen evolution reaction (OER: η20 = 293 mV). The addition of hydrazine to an alkaline electrolyte can decrease the cell voltage by 1.41 V when the current density is 20 mA cm−2, and achieve a high-speed hydrogen yield driven by an AA battery. This work puts forward an idea for the rational design of environmentally friendly and effective hybrid catalysts. [ABSTRACT FROM AUTHOR]

The requirement of hydrogen adsorption Gibbs free energy (ΔGH*) approximating to 0 eV limits the hydrogen evolution reaction (HER) activity of most electrocatalysts in alkaline media. The construction of interface and defects engineering is an effective strategy to obtain the optimal ΔGH*. Ni3N exhibits poor HER activity due to its undesirable ΔGH*. By cooperating with Nb2O5, the d-band center of Ni3N was reduced, improving its catalytic performance. The optimized Nb2O5–Ni3N displays an overpotential of 80 mV at 10 mA cm−2 and superior activity than the benchmark Pt/C catalyst when the current density is greater than 125 mA cm−2. Experimental and density functional theory results demonstrate that the improved catalytic activity is because the electronic interaction between Ni and Nb changes the coordination numbers of these two atoms, resulting in oxygen vacancies at the interface. Under the synergistic effect of Nb2O5 and Ni3N, the catalyst exhibits optimal ΔGH* and water adsorption energy. [ABSTRACT FROM AUTHOR]

Herein, we have synthesized successfully a three-dimensional/two dimensional (3D/2D) core–shell Cu2O@Fe–Ni3S2 nanoflower on copper foam at room temperature. Remarkably, by virtue of rich active sites and vacancies, large surface area, high conductivity and close contact with the electrolyte, the Cu2O@Fe–Ni3S2 catalyst exhibits superior stability and oxygen evolution reaction performance. [ABSTRACT FROM AUTHOR]

Efficient electrocatalysts require not only a tunable electronic structure but also great active site accessibility and favorable mass transfer. Here, a two-dimensional/three-dimensional (2D/3D) hierarchical electrocatalyst consisting of Co(OH) 2 -CeO 2 nanosheet-decorated Co dendrites is proposed, named as Co(OH) 2 -CeO 2 /Co. Based on the strong electronic interaction of the Co(OH) 2 -CeO 2 heterojunction, the electronic structure of the Co site is optimized, which facilitates the adsorption of intermediates and the dissociation of H 2 O. Moreover, the open 2D/3D structure formed by introducing the Co substrate further reduces the accumulation of heterogeneous nanosheets and promotes the radial diffusion of the electrolyte, significantly improving the utilization of active sites and shortening the electron transfer pathway. In addition, the superhydrophilic/superaerophobic interface achieved by constructing the hierarchical micro-nanostructure is beneficial to electrolyte infiltration and bubble desorption, thus ensuring favorable mass transfer. Therefore, Co(OH) 2 -CeO 2 /Co exhibits an excellent overall water-splitting activity in alkaline solution.

Electrochemical water splitting is widely studied in the hope of solving environmental deterioration and energy shortage. The design of inexpensive metal catalysts exhibiting desired catalytic performance and durable stability for efficient oxygen evolution is the pursuit of sustainable and clean energy fields. Herein, a three-dimensional (3D) flower-like NiSe 2 primary structure, modified with highly dispersed CuSe 2 nanoclusters as the secondary structure, is obtained by regulating the growth trend of the nanosheets. Benefiting from the metallicity of selenides and the formation of a heterogeneous interface, NiSe 2 @CuSe 2 /NF shows comparable performance toward the oxygen evolution reaction (OER) in an alkaline environment. Upon regulating the synthesis conditions, the catalyst exhibits its optimal performance with ultralow overpotential for the OER when the Ni/Cu molar ratio is 1 : 0.2 and the hydrothermal temperature and hydrothermal time are 200 °C and 6 h, respectively. It provides a current density of 10 mA cm -2 when a potential of 201 mV is applied without iR compensation. In this work, the hierarchical heterostructures of NiSe 2 and CuSe 2 are synthesized, which exhibit high electrocatalytic activity towards the oxygen evolution reaction and provides a new possibility for the extensive application of copper-based compounds in advanced energy fields.

Herein, we have synthesized successfully a three-dimensional/two dimensional (3D/2D) core-shell Cu 2 O@Fe-Ni 3 S 2 nanoflower on copper foam at room temperature. Remarkably, by virtue of rich active sites and vacancies, large surface area, high conductivity and close contact with the electrolyte, the Cu 2 O@Fe-Ni 3 S 2 catalyst exhibits superior stability and oxygen evolution reaction performance.