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Nitrate (NO3−), a nitrogen-containing pollutant, is prevalent in aqueous solutions, contributing to a range of environmental and health-related issues. The electrocatalytic reduction of NO3− holds promise as a sustainable approach to both eliminating NO3− and generating valuable ammonia (NH3). Nevertheless, the reduction reaction of NO3− (NO3−RR), involving 8-electron transfer process, is intricate, necessitating highly efficient electrocatalysts to facilitate the conversion of NO3− to NH3. In this study, Fedoped Co3O4 nanowire strutted three-dimensional (3D) pinewood-derived carbon (Fe-Co3O4/PC) is proposed as a high-efficiency NO3−RR electrocatalyst for NH3 production. Operating within 0.1 M NaOH containing NO3−, Fe-Co3O4/PC demonstrates exceptional performance, obtain an impressively large NH3 yield of 0.55 mmol·h−1·cm−2 and an exceptionally high Faradaic efficiency of 96.5% at −0.5 V, superior to its Co3O4/PC counterpart (0.2 mmol·h−1·cm−2, 73.3%). Furthermore, the study delves into the reaction mechanism of Fe-Co3O4 for NO3−RR through theoretical calculations. [ABSTRACT FROM AUTHOR]

The coordination microenvironment of metal active sites in metal–organic frameworks (MOFs) plays a crucial role in its performance for electrochemical CO2 reduction reaction (CO2RR). However, it remains a challenge to clarify the structure–performance relationship for CO2RR catalyzed by MOFs. Herein, a series of MOFs with different coordination microenvironments of Cu(I) sites (CuCl, CuBr, and CuI) to evaluate their performances for CO2RR is synthesized. With the increasing radius of halogen atom, the CO2 adsorption capacity increases and d‐band center of Cu positively shifts to the Fermi level, leading to enhance the selectivity of CO2 to CH4 conversion. CuI gives the highest total Faradaic efficiency (FE) of 83.2%, with a FE of CH4 up to 57.2% and CH4 partial current density of 60.7 mA cm−2 at −1.08 V versus reversible hydrogen electrode. Theoretical calculations reveal that the shifted d‐band center of Cu site contributes to reduced formation energies of *CH2O and *CH3O intermediates, which is the potential‐determining step of CO2RR and thus facilitates the electrocatalytic CO2 reduction to CH4. This study opens a new avenue for studying the relationship between the coordination microenvironment of active site and electroreduction reaction performance of MOFs. [ABSTRACT FROM AUTHOR]

Sustainable mitigation of the continuously rising concentration of NO contaminants is among the most urgent issues of this century. Ambient electrocatalytic conversion of NO into useful NH3 offers an attractive path toward achieving sustainable NO abatement and NH3 production simultaneously. However, its efficiency is challenged by the intense competition from hydrogen evolution reaction and relatively high energy barriers of NO activation. It is thus highly desirable to explore active electrocatalyst for NO reduction reaction and investigate the mechanisms on relevant surfaces. Herein, we introduce an FeP nanorod array on carbon cloth as a high-efficiency catalyst for NO electroreduction to NH3. In 0.2 M phosphate-buffered solution, this catalyst exhibits a low onset potential of −0.014 V. Moreover, it achieves a remarkable Faradaic efficiency of 88.49% and a large NH3 yield of 85.62 µmol·h−1·cm−2, with durability for stable NO conversion over 12 h of electrolysis. The catalytic mechanism on FeP is investigated further by theoretical calculations. [ABSTRACT FROM AUTHOR]

Purposefully developing crystalline materials at molecular level to improve the selectivity of electroreduction CO2 to CH4 is still rarely studied. Herein, a single crystal of copper(II) complex with hydroxy groups was designed and synthesized, namely 5,10,15,20‐tetrakis(3,4‐dihydroxyphenyl)porphyrin copper(II) (Cu‐PorOH), which could serve as a highly efficient heterogeneous electrocatalyst for electroreduction of CO2 toward CH4. In 0.5 m KHCO3, Cu‐PorOH gave a high faradaic efficiency of 51.3 % for CH4 and drove a partial current density of 23.2 mA cm−2 at −1.5 V versus the reversible hydrogen electrode in H‐cell. The high performance was greatly promoted by the hydroxy groups in Cu‐PorOH, which could not only form stable three‐dimensional frameworks through hydrogen‐bonding interactions but also stabilize the intermediate species by hydrogen bonds, as supported by density functional theory calculations. This work provides an effective avenue in exploring crystalline catalysts for CO2 reduction at molecular level. [ABSTRACT FROM AUTHOR]

[Display omitted] • Facile co-precipitation method yields efficient Co-doped graphdiyne catalysts. • Co-doped graphdiyne enhances NH 3 decomposition (100% conversion at 550 ℃). • NH x dehydrogenation (x = 3) is the rate-determining step on Co-doped graphdiyne. Manufacturing hydrogen from ammonia decomposition is an efficient and promising approach for hydrogen utilization. However, its scalable application is significantly impeded by the requirements of precious metal ruthenium (Ru) as catalysts. Herein, we report a type of Co-doped graphdiyne catalyst for catalytically decomposing ammonia (NH 3) to generate H 2. The metal-doped graphdiyne catalysts were synthesized facilely using co-precipitation approach. The resultant composite catalysts significantly enhanced the reactivity and stability of ammonia decomposition. The Co-doped graphdiyne catalyst achieved nearly complete decomposition of ammonia at 550 ℃, and the conversion rate remained stable over 18 h of continuous reaction. The adsorption and decomposition of ammonia by Co-doped graphdiyne was studied by density functional theory (DFT) calculations. Nitrogen binding strength was used as a descriptor to elucidate the catalyst's activity and reaction kinetics, further supported by the reaction energy barrier. Our study highlights the tremendous potential of metal-doped graphdiyne catalysts for facile hydrogen production via NH 3 decomposition, enabling safe and scalable hydrogen utilization. [ABSTRACT FROM AUTHOR]

It is of great importance to search for efficient and stable metal-free catalysts toward electrochemical N2-to-NH3 conversion. In this communication, a chemically oxidized carbon nanotube material (O-CNT) is verified as an active electrocatalyst for the N2 reduction reaction under ambient conditions. In 0.1 M LiClO4, O-CNT achieves a large NH3 yield of 32.33 μg h−1 mgcat.−1 and a high faradaic efficiency of 12.50% at −0.4 V vs. the reversible hydrogen electrode. It also demonstrates superior stability. Density functional theory calculations suggest that C–O groups play a key role in the electrochemical N2 fixation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A strategy to design metal-free catalyst for nitric oxide reduction is developed. • Molecular orbital theory and band theory are combined to study catalytic mechanism. • A particular C center -CN 2 active site on hBN-graphene interface is discovered. • The high-activity C center -CN 2 configuration is applicable to other 2D materials. Electrochemical reduction reaction of nitric oxide (NORR) to ammonia has been considered as a promising alternative to capturing and utilizing NO emitted from thermal-power plants. Various metal-containing catalysts have been proved to possess efficient catalytic activities for NORR, yet the attempt on metal-free NORR catalysts is quite limited. Herein, by employing first-principle calculations, we propose a novel strategy of designing metal-free NORR catalyst by introducing C center -CN 2 configuration into hexagonal boron nitride-graphene heterostructures (hBN-graphene). The hBN-graphene heterostructures demonstrate excellent NORR activity, achieving a fairly low limiting potential of −0.22 V. The superior NORR activity is ascribed to the introduced unique configuration at the modified hBN-graphene interface. Moreover, the hBN-graphene heterostructures can efficiently suppress hydrogen evolution—the main competitive reaction. The ab-initio molecular dynamic simulations indicate that hBN-graphene heterostructures can retain considerable thermal stability. Our work opens an avenue to design metal-free catalysts for NORR by modulating the interface in two-dimensional heterostructures. [ABSTRACT FROM AUTHOR]

Harvesting water and energy from ambient environment promises to relieve the worldwide fresh-water scarcity and energy shortage. The fabrication of well-designed materials for atmospheric water harvesting (AWH) requires highly-technical skills, hampering practical applications in isolated regions or after natural disasters. Herein, we report an efficient moisture absorber from waste corn stalk for AWH and for concurrent electricity generation. The sample can adsorb water at capacities of 0.46–1.84 kg kg−1 under relative humidity of 20%–80%. Moreover, with surface modification using commercial carbon ink, a corn stalk slice (3 cm × 1 cm × 0.2 cm) can output a stable open-circuit voltage of ~0.6 V in the air. Density functional theory calculations reveal that the oxygen groups in the carbon ink contribute to the power generation in the corn stalk. When connected in series, corn stalk slices can directly power an electronic calculator. This study contributes to the development of practical strategies to address issues in the water-waste-energy nexus. Image 1 • Waste corn stalk based moisture absorber was developed for atmospheric water harvesting and electricity generation. • The moisture absorber delivered water harvesting capacities of 0.46–1.84 kg kg−1 under relative humidity of 20%–80%. • The corn stalk with size of 3 cm × 1 cm × 0.2 cm generated a stable voltage of ~0.6 V for over 40 h in the air. • 3 corn stalks connected in series could power an electronic calculator in the atmosphere. [ABSTRACT FROM AUTHOR]

Ru-doped TiO 2 nanoribbon array supported on Ti plate acts as an efficient catalyst for NH 3 synthesis via electrochemical NO 2 − reduction, obtaining an ultra-large NH 3 yield of 1.56 mmol h−1 cm−2 and a super-high Faradaic efficiency of 98.9%. [Display omitted] • Ru doping is shown as an effective strategy to boost NO 2 −-to-NH 3 conversion over TiO 2 nanoribbon array supported on Ti plate. • Ru–TiO 2 /TP achieves an ultra-large NH 3 yield of 1.56 mmol h−1 cm−2 and a super-high Faradaic efficiency of 98.9% with long-term electrolytic durability. • DFT calculations reveal the catalytic mechanism of NO 2 –RR on Ru–TiO 2. Electrochemical reduction of nitrite (NO 2 –) not only removes NO 2 – contaminant but also produces high-added value ammonia (NH 3). This process, however, needs efficient and selective catalysts for NO 2 −-to-NH 3 conversion. In this study, Ruthenium doped titanium dioxide nanoribbon array supported on Ti plate (Ru–TiO 2 /TP) is proposed as an efficient electrocatalyst for the reduction of NO 2 − to NH 3. When operated in 0.1 M NaOH containing NO 2 –, such Ru–TiO 2 /TP achieves an ultra-large NH 3 yield of 1.56 mmol h−1 cm−2 and a super-high Faradaic efficiency of 98.9%, superior to its TiO 2 /TP counterpart (0.46 mmol h−1 cm−2, 74.1%). Furthermore, the reaction mechanism is studied by theoretical calculation. [ABSTRACT FROM AUTHOR]

The coordination microenvironment of metal active sites in metal–organic frameworks (MOFs) plays a crucial role in its performance for electrochemical CO2 reduction reaction (CO2RR). However, it remains a challenge to clarify the structure–performance relationship for CO2RR catalyzed by MOFs. Herein, a series of MOFs with different coordination microenvironments of Cu(I) sites (CuCl, CuBr, and CuI) to evaluate their performances for CO2RR is synthesized. With the increasing radius of halogen atom, the CO2 adsorption capacity increases and d‐band center of Cu positively shifts to the Fermi level, leading to enhance the selectivity of CO2 to CH4 conversion. CuI gives the highest total Faradaic efficiency (FE) of 83.2%, with a FE of CH4 up to 57.2% and CH4 partial current density of 60.7 mA cm−2 at −1.08 V versus reversible hydrogen electrode. Theoretical calculations reveal that the shifted d‐band center of Cu site contributes to reduced formation energies of *CH2O and *CH3O intermediates, which is the potential‐determining step of CO2RR and thus facilitates the electrocatalytic CO2 reduction to CH4. This study opens a new avenue for studying the relationship between the coordination microenvironment of active site and electroreduction reaction performance of MOFs. [ABSTRACT FROM AUTHOR]

• A hierarchical porous Indium-doping ZnO micro-bowl is constructed through an in-situ corrosion method. • The abundant voids and nanopores facilitate the ionic transport and accommodating the volumetric changes. • The Indium-doping accelerates the transition kinetics between Zn and ZnO through enhancing the electrical/ionic conductivity and adsorption to OH–. • The Indium-doping inhibits the hydrogen evolution. • The In-ZnO demonstrates high Zn utilization of 92.3%, and high capacity of 590.2 mAh/g even at high current density of 36 A/g. Aqueous nickel-zinc (Ni-Zn) battery is one promising grid energy storage device owing to its high theoretical energy density, high safety and low cost. However, the large-scale commercialization of Ni-Zn battery is significantly hindered by its low practical energy density and poor cycle lifespan caused by the low reversibility and transition kinetics between the metallic Zn and ZnO with low Zn utilization. To address these issues, a type of hierarchical porous Indium-doping ZnO micro-bowls (In-ZnO) is constructed through an in-situ chemical corrosion strategy. The abundant voids and pores facilitate the ionic transport, and simultaneously accommodate the volumetric expansion during the electrochemical transition between metallic Zn and ZnO. Density functional theory calculations further reveal that In-ZnO achieves the enhanced electrical/ionic conductivity and improved adsorption to OH–, accelerating the solid–liquid transitions of Zn-Zn(OH) 4 2- and Zn(OH) 4 2--ZnO, as well as the solid–solid transition of Zn-ZnO. Simultaneously, the Indium-doping inhibits the hydrogen evolution and passivation. Ascribed to the synergetic effect of the hierarchical porous structure and Indium-doping, the In-ZnO electrode demonstrates ultra-stable capacity retention of 98.6% over 1000 cycles at 9 A g-1 under 92.3% Zn utilization, and high capacity of 590.2 mAh g-1 even at high current density of 36 A g-1. [ABSTRACT FROM AUTHOR]

As a high-active metal-free electrocatalyst for NH 3 production via NO reduction reaction, honeycomb carbon nanofiber achieves an NH 3 yield of 22.35 μmol h−1 cm−2 with a high Faradaic efficiency of 88.33%. [Display omitted] Electrocatalytic NO reduction is a promising technology for ambient NO removal with simultaneous production of highly value-added NH 3. Herein, we report that honeycomb carbon nanofiber coated on carbon paper acts as an efficient metal-free catalyst for ambient electroreduction of NO to NH 3. In 0.2 M Na 2 SO 4 solution, such catalyst achieves an NH 3 yield of 22.35 μmol h−1 cm−2 with a high Faradaic efficiency of up to 88.33%. Impressively, it also shows excellent stability for 10-h continuous electrolysis. Theoretical calculations reveal that the most active center of functional groups is –OH group for NO reduction with a low energy barrier (ΔG of 0.29 eV) for the potential-determining step (*NO + H → *HNO). [ABSTRACT FROM AUTHOR]

• A low corrosive but highly efficient activation method by using K 2 C 2 O 4 and urea. • Urea lowers the activation temperature and initiates a second-step gas-exfoliation. • The enhanced gas-exfoliation leads to high surface area and sheet-like structure. • Porous carbon performs well in aqueous and quasi-solid zinc ion hybrid supercapacitors. • The interaction between N- and O-containing groups for zinc ion storage was studied. Porous carbons are the favorable candidate cathode for the emerging zinc ion hybrid supercapacitors (ZHSCs). The scale-up production of porous carbon requires green synthesis methods to replace the existing corrosive KOH activation, but most mild activators suffer from low activation efficiency, leading to the inferior surface area and capacitance. Herein, we propose a urea-boosted gas-exfoliation method using K 2 C 2 O 4 as the mild activator and lignin as the low-cost precursor. Urea has the auxo-action to lower the decomposing temperature of K 2 C 2 O 4 and to initiate an extra second-step gas-exfoliation. The auxo-action produces the enlarged surface area of porous carbon from 592 m2/g to 1949 m2/g and promotes the morphology regulation from thick carbon bulks to layered carbon sheets. The improved carbon structure contributes to the excellent capacitive performance with a high energy-power density of 126.71 Wh kg−1 at 79.37 W kg−1. Moreover, the energy-storage mechanism is studied by both electrochemical analysis and Density Functional Theory (DFT) method. The DFT calculation demonstrates the effect of interaction between N- and O-containing groups on the adsorption capacity of zinc ions, which can provide information for the structural optimization design of carbon cathode. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3) has been regarded as an attractive energy source for hydrogen production via catalytic decomposition, especially over non-noble metal catalysts. Owing to the decent performance and low cost, nickel (Ni) based catalysts have been widely studied for catalytic decomposition of NH 3 where the decomposition rates, can be further tailored by adding other metals. Herein, we synthesized bimetallic M(M = Co, Fe, Cu)Ni/Al 2 O 3 catalysts delivering superior catalytic performance at a wide temperature range of 350–750 °C. Co-Ni/Al 2 O 3 demonstrated nearly 100% conversion of NH 3 decomposition to H 2 at 700 °C and the gas hourly space velocity of 30,000 ml g−1 min−1, which was ~20.85% higher than that of intrinsic Ni/Al 2 O 3. The structural characterizations indicated that Co could decrease the particle size and enhance the dispersion of active sites. The density functional theory calculations substantiated that the associative decomposition of N to generate N 2 was the rate-determining step of the NH 3 decomposition reactions. NH 3 Temperature Programmed Desorption (TPD) results suggested that the enhanced catalytic performance was predominantly attributed to the Co that decreases the energy barrier for the associative decomposition of N to form N 2. This study provides new insights in designing diverse catalysts for efficient NH 3 decomposition for controllable H 2 production. • Various biometallic M(M = Co, Fe, Cu)Ni/Al 2 O 3 catalysts were developed for NH 3 decomposition. • The associative decomposition of N to form N 2 was determined to be the rate-limiting step. • Co dopant lowered the energy barrier for the associative decomposition of N in Ni/Al 2 O 3 • Enhanced NH 3 decomposition performance was obtained by using CoNi/Al 2 O 3. [ABSTRACT FROM AUTHOR]