Electrochemical nitrate reduction reaction (NO₃RR) is a promising means for generating the energy carrier ammonia. Herein, we report the synthesis of heterostructure copper-nickel phosphide electrocatalysts via a simple vapor-phase hydrothermal method. The resultant catalysts were evaluated for electrocatalytic nitrate reduction to ammonia (NH₃) in three-type electrochemical reactors. In detail, the regulation mechanism of the heterogeneous Cu₃P-Ni₂P/CP-x for NO₃RR performance was systematically studied through the H-type cell, rotating disk electrode setup, and membrane-electrode-assemblies (MEA) electrolyzer. As a result, the Cu₃P-Ni₂P/CP-0.5 displays the practicability in an MEA system with an anion exchange membrane, affording the largest ammonia yield rate (R_NH3) of 1.9 mmol·h⁻¹·cm⁻², exceeding most of the electrocatalytic nitrate reduction electrocatalysts reported to date. The theoretical calculations and in-situ spectroscopy characterizations uncover that the formed heterointerface in Cu₃P-Ni₂P/CP is beneficial for promoting nitrate adsorption, activation, and conversion to ammonia through the successive hydrodeoxygenation pathway.

Here we report a vapor-phase reaction approach to fabricate rhodium(I)-dodecanethiol complex coated on carbon fiber cloth (Rh(I)-SC₁₂H₂₅/CFC), followed by low-temperature pyrolysis to achieve dodecanethiol modified Rh (Rh@SC₁₂H₂₅/CFC) for electrocatalytic nitrogen reduction reaction (NRR). The results demonstrate that after pyrolysis for 0.5 h at 150 °C, the obtained Rh@SC₁₂H₂₅/CFC-0.5 exhibits excellent NRR activity with an NH₃ yield rate of 121.2 ± 6.6 µg∙h⁻¹∙cm⁻² (or 137.7 ± 7.5 µg∙h⁻¹∙mg_Rh⁻¹) and a faradaic efficiency (FE) of 51.6% ± 3.8% at −0.2 V (vs. RHE) in 0.1 M Na₂SO₄. The theoretical calculations unveil that the adsorption of dodecanethiol on the hollow sites of Rh(111) plane is thermodynamically favorable, effectively regulating the electronic structure and surface wettability of metallic Rh. Importantly, the dodecanethiol modification on Rh(111) obviously decreases the surface H* coverage, thus inhibiting the competitive hydrogen evolution reaction and concurrently reducing the electrocatalytic NRR energy barrier.

Manganese tetravalent oxide (MnO₂), a superstar Faradic electrode material, has been investigated extensively for capacitive desalination, enabling higher salt adsorption capacity compared to the great majority of carbonous electrodes. However, few works paid attention on the relationship between the valences of manganese oxide and their desalination performance. For the first time, we prepared the spindle-like manganese oxides/carbon composites with divalent (MnO@C), trivalent (Mn₂O₃@C) and divalent/ trivalent (Mn₃O₄@C) manganese by pyrolysis of manganese carbonate precursor under different condition, respectively. The electrochemical behavior in three-electrode system and electrosorption performance obtained in hybrid membrane capacitive deionization (HMCDI) cells assembled with capacitive carbon electrodes were systematically evaluated, respectively. High salt adsorption capacity (as large as 31.3, 22.2, and 18.9 mg·g^–1) and corresponding average salt adsorption rates (0.83, 0.53, and 1.71 mg·g^–1·min^–1) were achieved in 500 mg·L^–1 NaCl solution for MnO@C, Mn₂O₃@C, and Mn₃O₄@C, respectively. During fifteen electrosorption-desorption cycles, ex-situ water contact angle and morphology comparison analysis demonstrated the superior cycling durability of the manganese oxide electrodes and subtle difference between their surface redox. Furthermore, density functional theory (DFT) was also conducted to elaborate the disparity among the valence states of manganese (+2, +3 and +2/+3) for in-depth understanding. This work introduced manganese oxide with various valences to blaze new trails for developing novel Faradic electrode materials with high-efficiency desalination performance by valence engineering.

Electrochemical water splitting is quite seductive for eco-friendly hydrogen fuel energy production, however, the attainment of highly efficient, durable, and cheap catalysts for the hydrogen evolution reaction (HER) remains challenging. In this study, molybdenum oxides stabilized palladium nanoparticle catalysts (MoO_x-Pd) are in situ prepared on commercial carbon cloth (CC) by the facile two-step method of dip-coating and electrochemical reduction. As a self-supported Pd-based catalyst electrode, the MoO_x-Pd/CC presents a competitive Tafel slope of 45.75 mV·dec^-1, an ultralow overpotential of 25 mV, and extremely long cycling durability (one week) in 0.5 M H₂SO₄ electrolyte, superior to unmodified Pd catalysts and comparable to commercial Pt mesh electrode. On the one hand, the introduction of MoO_x can inhibit the growth of Pd particles to obtain ultrafine Pd nanoparticles, thus exposing more available active sites. On the other hand, density functional theory (DFT) calculation revealed that MoO_x on the surface of Pd metal can regulate the electronic structure of Pd metal and enhance its intrinsic catalytic activity of HER. This work suggests that transitional metal nanoparticles stabilized by molybdenum oxides are hopeful approaches for obtaining fruitful hydrogen-producing electrocatalysts.

Electrocatalytic synthesis of value-added chemicals is attracting significant research attention owing to its mild reaction conditions, environmental benignity, and potentially scalable application to organic synthetic chemistry. Herein, we report the preparation of a single-crystalline NiS₂ nanostructure film of ~ 50 nm thickness grown directly on a carbon fiber cloth (NiS₂/CFC) by a facile vapor-phase hydrothermal (VPH) method. NiS₂/CFC as an electrocatalyst exhibits activity for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in alkaline media. Furthermore, a series of alcohols (2-propanol, 2-butanol, 2-pentanol, and cyclohexanol) were electrocatalytically converted to the corresponding ketones with high selectivity, efficiency, and durability using the NiS₂/CFC electrode in alkaline media. In the presence of 0.45 M alcohol, a remarkably decreased overpotential (~ 150 mV, vs. RHE) at the NiS₂/CFC anode compared with that for water oxidation to generate O₂, i.e., the OER, in alkaline media leads to significantly improved H₂ generation. For instance, the H₂ generation rate in the presence of 0.45 M 2-propanol is almost 1.2-times of that obtained for pure water splitting, but in a system that employs an applied voltage at least 280 mV lower than that required for water splitting to achieve the same current density (20 mA·cm^–2). Thus, our results demonstrate the applicability of our bifunctional non-precious-metal electrocatalyst for organic synthesis and simultaneous H₂ production.

Electrocatalysts with high catalytic activity and stability play a key role in promising renewable energy technologies, such as fuel cells and metal-air batteries. Here, we report the synthesis of Fe/Fe₂O₃ nanoparticles anchored on Fe-N-doped carbon nanosheets (Fe/Fe₂O₃@Fe-N-C) using shrimp shell-derived N-doped carbon nanodots as carbon and nitrogen sources in the presence of FeCl₃ by a simple pyrolysis approach. Fe/Fe₂O₃@Fe-N-C obtained at a pyrolysis temperature of 1, 000 ℃ (Fe/Fe₂O₃@Fe-N-C-1000) possessed a mesoporous structure and high surface area of 747.3 m²·g^-1. As an electrocatalyst, Fe/Fe₂O₃@Fe-N-C-1000 exhibited bifunctional electrocatalytic activities toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media, comparable to that of commercial Pt/C for ORR and RuO₂ for OER, respectively. The Zn-air battery test demonstrated that Fe/Fe₂O₃@Fe-N-C-1000 had a superior rechargeable performance and cycling stability as an air cathode material with an open circuit voltage of 1.47 V (vs. Ag/AgCl) and a power density of 193 mW·cm^-2 at a current density of 220 mA·cm^-2. These performances were better than other commercial catalysts with an open circuit voltage of 1.36 V and a power density of 173 mW·cm^-2 at a current density of 220 mA·cm^-2 (a mixture of commercial Pt/C and RuO₂ with a mass ratio of 1:1 was used for the rechargeable Zn-air battery measurements). This work will be helpful to design and develop low-cost and abundant bifunctional oxygen electrocatalysts for future metal-air batteries.