Enhanced active hydrogen supply promotes interfacial tandem electrocatalytic nitrate reduction to ammonia.

Hypes and hopes on the materials development strategies to produce ammonia at mild conditions

The electrocatalytic nitrate reduction reaction (NO3RR) offers a sustainable route for ammonia synthesis while addressing nitrate pollution, yet it faces challenges such as sluggish kinetics, competing hydrogen evolution reaction (HER), and poor selectivity under high current densities. Herein, we report a phosphorus-doped Co(OH)2/Cu nanowire (P-Co(OH)2/Cu NW) tandem catalyst engineered via in situ reconstruction, which achieves exceptional NO3RR performance through synergistic dual-site mechanisms. The Cu phase promotes NO3- adsorption and activation, Co(OH)2 facilitates ammonia formation, while P doping induces water dissociation to generate *H for hydrogenation instead of H2 evolution. In 1 M KOH + 0.1 M NO3-, the catalyst delivers a record ammonia yield of 110.14 mg h-1 cm-2 with 95.13% Faradaic efficiency at -0.8 V vs RHE and industrially relevant current densities (-1 A cm-2 at -0.55 V). In situ spectroscopic studies reveal that P doping modulates interfacial water structure, accelerating *H generation and optimizing the tandem pathway. Further, a Zn-NO3- battery integrating this cathode achieves simultaneous power output (28.4 mW cm-2) and ammonia production (6.65 mg h-1 cm-2, FE: 90.8%), demonstrating its practical viability.

Refractory metals possess unique properties including high melting points, high hardness at room temperature, chemical resistance, and high density. Electrodeposition of refractory metals is of interest as a scalable approach to apply uniform coatings to enable a wide range of applications in aerospace, nuclear, catalysis, biomedical fields. This talk will focus on pulse electrochemical variables to enable methods to electrodeposit high quality metallic rhenium (Re).Re has traditionally been difficult to deposit from aqueous solutions due to the over potential for hydrogen evolution and complex electrochemical reactions. Electrodeposition of rhenium usually occurs from the perrhenate ion (ReO4-) with an oxidation state of +7. The exact mechanism to reduce the perrhenate ion from +7 to metallic rhenium is still unknown. It is unlikely that the 7 electrons transfer in a single step, so reduction likely occurs through intermediate oxide species including ReO2, ReO3 and Re2O5. Combined with the hydrogen evolution reaction, Re coatings are generally deposited at low faradaic efficiency, are brittle, and limited in thickness (sub-micron). In our previous work, water-in-salt electrolytes and complexing additives have enabled resolution of some of the issues associated with this complexity and a range of deposit qualities, though cracking issues remain and coating quality issues still needed optimization.Herein, we present on the effects of pulsed electrochemical approaches to eliminate cracking in the film by balancing nucleation and growth and the competing hydrogen evolution reaction. A custom high-throughput cell was developed to rapidly screen parameters and explore time-dependent evolution of the electrodeposition processes.

<p>Electrochemical nitrogen reduction reaction (eNRR) is a promising sustainable alternative to the energy-intensive Haber–Bosch process for ammonia (NH₃) synthesis. However, simultaneously achieving high activity and selectivity remains challenging due to competing hydrogen evolution reaction (HER). In this study, a series of copper sulfide catalysts were investigated for eNRR under ambient conditions. Copper sulfides featuring highly crystalline low-index (1 1 1) facets exhibited significant NH₃ production; however, the presence of high-index facets led to a reduction in Faradaic efficiency (F.E.) due to their higher activity toward the competing HER. To mitigate this intrinsic trade-off between activity and selectivity, bromide ions were introduced to selectively adsorb onto the high-index planes, effectively suppressing HER. Optimizing the bromide ion coverage on CuSₓ catalysts resulted in a maximum NH3 yield of 1.2 μmol h–¹ cm–² (JNH3 = 0.198 mA/cm2) and a F.E. of 23.34% at −0.6 VRHE, marking improvements of 84.0% in activity and 316% in selectivity compared to untreated catalysts. It was verified that bromide ions selectively passivate HER-prone surfaces without blocking the active sites responsible for nitrogen adsorption. This study highlights that facet-selective surface engineering using halide ions can simultaneously enhance both activity and selectivity in eNRR. It provides a rational design principle for improving catalytic performance in complex reaction environments where multiple pathways compete.</p>

Boosting C–C coupling to multicarbon products via high-pressure CO electroreduction

We present a controlled fabrication of selective ultrathin metal–organic framework (MOF) nanosheets as preassembling platforms, yolk–shell structured with a few-layered N-doped carbon (NC) shell-en...

Electrocatalytic hydrogenation of toxic nitrobenzene to value-added aniline is of great significance in addressing the issues of energy crisis and environmental pollution. However, it is a considerable challenging and crucial to develop highly efficient and earth-abundant transition metal-based electrocatalysts with superior durability for the electro-hydrogenation of nitrobenzene due to the competitive hydrogen evolution reaction (HER). In this work, a facile approach is designed and introduced to constructing an integrated self-supported heterostructured Co1- xNix(OH)(CO3)/Al(OH)3 nanoarrays (CoNiCH/Al(OH)3) for the electrocatalytic reduction of nitrobenzoic acid (PNBA) to p-aminobenzoic acid (PABA) and its electrocatalytic mechanism for PNBA reduction is investigated. This unique Lewis acid-base pairs with abundant oxygen vacancies (OVs) can effectively regulate the adsorption energy of PNBA and active hydrogen intermediates, facilitate the proton-coupled electrocatalytic reduction process, leading to the high activity and selectivity for PNBA to PABA. The optimal CoNiCH/Al(OH)3-0.5 exhibits outstanding performance for the electrocatalytic hydrogenation of PNBA to PABA with a yield of 92%, selectivity of 95% and Faraday efficiency (FE) of 92% at -0.545V (vs reversible hydrogen electrode, RHE) under 0.1m phosphate buffered solution (PBS) neutral electrolyte. Besides, it can maintain a high electrocatalytic activity for at least eight electrocatalytic cycle-test.

Bismuth-based materials have been recognized as promising catalysts for the electrocatalytic CO2 reduction reaction (ECO2RR). However, they poor selectivity due to competing hydrogen evolution reaction (HER) remains challenging. In this study, we have developed an edge defect modulation strategy for Bi by coordinating the edge defects of bismuth (Bi) with sulfur, to promote ECO2RR selectivity and inhibit the competing HER. The prepared catalysts demonstrate excellent product selectivity, with a high HCOO- Faraday efficiency of ~95% and an HCOO- partial current of ~250 mA cm-2 under alkaline electrolytes. Density function theory calculations reveal that sulfur tends to bind to the Bi edge defects, reducing the coordination-unsaturated Bi sites (*H adsorption sites), and regulating the charge states of neighboring Bi sites to improve *OCHO adsorption. This work deepens our understanding of ECO2RR mechanism on bismuth-based catalysts, guiding for the design of advanced ECO2RR catalysts.

Bismuth‐based materials have been recognized as promising catalysts for the electrocatalytic CO2 reduction reaction (ECO2RR). However, they show poor selectivity due to competing hydrogen evolution reaction (HER). In this study, we have developed an edge defect modulation strategy for Bi by coordinating the edge defects of bismuth (Bi) with sulfur, to promote ECO2RR selectivity and inhibit the competing HER. The prepared catalysts demonstrate excellent product selectivity, with a high HCOO− Faraday efficiency of ≈95 % and an HCOO− partial current of ≈250 mA cm−2 under alkaline electrolytes. Density function theory calculations reveal that sulfur tends to bind to the Bi edge defects, reducing the coordination‐unsaturated Bi sites (*H adsorption sites), and regulating the charge states of neighboring Bi sites to improve *OCHO adsorption. This work deepens our understanding of ECO2RR mechanism on bismuth‐based catalysts, guiding for the design of advanced ECO2RR catalysts.

Harnessing in-situ oxidation of nanostructured mxene to modulate the electronic structure for improved selectivity for electrochemical carbon dioxide reduction

• A Python model for semi-islanded green ammonia production was developed. • The LCOA ranges from 669.30 to 867.94 €/tNH 3 . • Power generation represents the largest share of total system costs. • The LCOA decreases by up to 15.15 % over the next two decades. • Dynamic operation achieves up to a 6 % reduction compared with continuous operation. The study presents a technical and economic assessment of green ammonia production in several counties in Ireland. The system is based on renewable energy sources, namely photovoltaic and offshore wind. Three locations were chosen based on their renewable potential and the availability of export ports to EU (European Union) markets. A high-temporal-resolution model for green ammonia production has been developed for the first time in Ireland. The WSA (Wind Solar Ammonia) model was developed specifically for this research. It uses MILP (Mixed Integer Linear Programming) and optimisation techniques to simulate scenarios at the lowest possible cost. The Python-based model incorporates all relevant energy subsystems and use functions from specialised libraries. The WSA model includes large-scale hydrogen production with proton exchange membrane electrolysers, air separation to produce nitrogen, Haber-Bosch ammonia synthesis, desalination unit. Storages buffers were implemented for green hydrogen, green ammonia, purified sea water, and nitrogen. Both continuous and dynamic operation were simulated, continuous operation reflects industrial reliability, stable equipment performance, and maximised lifetime, while dynamic operation captures renewable intermittency, curtailment reduction, and system flexibility. Cork is identified as the least-cost location, with the dynamic operation system achieving the lowest LCOA (Levelised Cost Of Ammonia) at 791.07 €/t in 2030 and 731.45 €/t in 2040, outperforming the continuous operation system, which records 834.27 €/t in 2030 and 741.62 €/t in 2040. The system achieve a carbon saving up to 94.63 % compared to the ammonia fossil fuel-based comparator.

N-modulated Cu0-Cu+ sites for C1/C2 selectivity regulation of carbon dioxide electrocatalytic reduction

The oxidation states of metal-based electrocatalysts have been proved to be beneficial to improve the product selectivity for electrochemical CO2 reduction (ECO2R), while it usually suffers from decay due to the reductive environment leading to performance deterioration. Herein, we construct robust Sn/SnO2 Mott–Schottky heterojunction on biomass (sodium alginate)-derived carbon by a facile heat treatment method, which demonstrates high selectivity and robustness for formate production by ECO2R. The wide partial current density of formate from 4.4 to 220.8 mA cm–2 with excellent formate selectivity (Faradaic efficiency (FE) > 90%) can be achieved on Sn/SnO2 heterojunction electrocatalyst in a gas diffusion flow cell, which is one of the widest among Sn-based electrocatalysts. Moreover, the Sn/SnO2 heterojunction electrocatalyst achieves a remarkably high total energy efficiency of 68.1% for formate production in a gas diffusion full cell. In situ Raman spectra and density functional theory simulations illustrate that the electrons transfer from SnO2 to Sn, which facilitates the formation of *OCHO intermediate meanwhile impeding the competitive hydrogen evolution reaction (HER), leading to the high selectivity and robustness for ECO2R.

The electrochemical synthesis of ammonia under ambient condition has attracted significant attention as an alternative route for green ammonia production. However, competing hydrogen evolution reaction (HER) hinders selective ammonia synthesis through electrochemical nitrogen reduction reaction (NRR). For the broad adoption of such technology in industries, it is essential to overcome poor selectivity of NRR by developing effective electrocatalysts and controlling the reactant at the interface between electrode and electrolyte.[1,2] In this study, we prepared cobalt-molybdenum carbide-carbon nanofiber via electrospinning method as a selective NRR catalyst. Furthermore, we reveal the relationship between water adsorption ability and NRR selectivity on biphasic catalyst using isotopic-labeling and in-situ analyses. Reference [1] Journal of Electroanalytical Chemistry 2021, 896, 115157.[2] Journal of Energy Chemistry 2022, 67, 474–482.

Due to the competitive relationship between nitrate reduction reaction (NO3 -RR) and hydrogen evolution reaction (HER), the conventional approach to improve Faradaic efficiency is to select a catalyst without HER activity. Nevertheless, such a strategy not only limits the application of HER catalysts in NO3 -RR, but also causes insufficient hydrogen source, thereby sacrificing ammonia yield rate. We believe that HER catalysts should not be excluded from hydrogenation reduction. Herein, taking traditional water electrolysis material Co3O4 as model system, we reveal that the oxygen vacancies on crystal facet can greatly promote water dissociation and capture HER intermediate for NO3 -RR, successfully shifting the reaction pathway from hydrogen evolution to nitrate hydrogenation. Beyond material development, we construct a hybrid reactor and achieve an ammonia recovery rate of 1216.8g-Nm-2d-1 in nuclear industry wastewater with ultra-high nitrate concentration. This study breaks through the limitation of HER catalyst in NO3 -RR, which provides a significant insight into the catalyst designing and hydrogenation mechanism.