To enable an efficient and cost‐effective electrocatalytic N2 reduction reaction (NRR) the development of an electrocatalyst with a high NH3 yield and good selectivity is required. In this work, ...Ti3C2Tx MXene‐derived quantum dots (Ti3C2Tx QDs) with abundant active sites enable the development of efficient NRR electrocatalysts. Given surface functional groups play a key role on the electrocatalytic performance, density functional theory calculations are first conducted, clarifying that hydroxyl groups on Ti3C2Tx offer excellent NRR activity. Accordingly, hydroxyl‐rich Ti3C2Tx QDs (Ti3C2OH QDs) are synthesized as NRR catalysts by alkalization and intercalation. This material offers an NH3 yield and Faradaic efficiency of 62.94 µg h−1 mg−1cat. and 13.30% at −0.50 V, respectively, remarkably higher than reported MXene catalysts. This work demonstrates that MXene catalysts can be mediated through the optimization of both QDs sizes and functional groups for efficient ammonia production at room temperature.
Hydroxyl‐rich MXene Ti3C2Tx quantum dots (Ti3C2OH QDs) are rationally designed for electrochemical nitrogen fixation. This material possesses increased active sites (Ti‐edge) and optimized surface functional groups (OH) based on the computational effort. The electrocatalyst exhibits high performance and excellent selectivity synchronously with the NH3 yield and Faradaic efficiency of 62.94 µg h−1 mg−1cat. And 13.30% at −0.50 V, respectively.
The synthesis of NH3 heavily depends on the energy-intensive Haber–Bosch process with a large amount of greenhouse gas emission. Electrochemical reduction offers a carbon-neutral process to convert ...N2 to NH3 at ambient conditions, but requires efficient and stable catalysts for the N2 reduction reaction. Mo-dependent nitrogenases and synthetic molecular complexes have attracted increasing attention for N2 fixation; however, less attention has been paid to Mo-based nanocatalysts for electrochemical N2 conversion to NH3. Herein, we report that MoO3 nanosheets act as an efficient non-noble-metal catalyst for electrochemical N2 fixation to NH3 with excellent selectivity at room temperature and atmospheric pressure. In 0.1 M HCl, this catalyst exhibits remarkable NRR activity with an NH3 yield of 4.80 × 10−10 mol s−1 cm−2 (29.43 μg h−1 mgcat.−1) and a faradaic efficiency of 1.9%. Moreover, this catalyst also shows high electrochemical stability and durability. Density functional theory calculations reveal that the outermost Mo atoms serve as the active sites for effective N2 adsorption.
Metal borides/borates have been considered promising as oxygen evolution reaction catalysts; however, to date, there is a dearth of evidence of long-term stability at practical current densities. ...Here we report a phase composition modulation approach to fabricate effective borides/borates-based catalysts. We find that metal borides in-situ formed metal borates are responsible for their high activity. This knowledge prompts us to synthesize NiFe-Boride, and to use it as a templating precursor to form an active NiFe-Borate catalyst. This boride-derived oxide catalyzes oxygen evolution with an overpotential of 167 mV at 10 mA/cm
in 1 M KOH electrolyte and requires a record-low overpotential of 460 mV to maintain water splitting performance for over 400 h at current density of 1 A/cm
. We couple the catalyst with CO reduction in an alkaline membrane electrode assembly electrolyser, reporting stable C
H
electrosynthesis at current density 200 mA/cm
for over 80 h.
Transition metal phosphides have been recognized as promising electrocatalysts for oxygen evolution reaction (OER) due to their low cost and high activity. However, the insufficient exposed active ...region limited the OER performance. Recently, the introduction of sacrificial dopants has been considered an effective strategy to enlarge the surface area. Herein, the Zn dopants are introduced in NiFe phosphide (NiFeZnP) nanosheet, which work as the sacrificial dopants to generate more exposed active NiFe sites and promote the formation of the NiFeOOH active phase during OER process. The optimized Zn-doped NiFeP catalyst shows an overpotential of ≈203 mV to reach a current density of 10 mA cm−2 in 1 M KOH, and a stability of 100 h at 1000 mA cm−2. Overall, this work provides a sacrificial Zn doping strategy to prepare highly efficient OER electrocatalysts.
Transition metal phosphides have been recognized as promising electrocatalysts for oxygen evolution reaction (OER) due to their low cost and high activity. However, the insufficient exposed active region limited the OER performance. Recently, the introduction of sacrificial dopants has been considered an effective strategy to enlarge the surface area. Herein, the Zn dopants are introduced in NiFe phosphide (NiFeZnP) nanosheet, which work as the sacrificial dopants to generate more exposed active NiFe sites and promote the formation of the NiFeOOH active phase during OER process. The optimized Zn-doped NiFeP catalyst shows an overpotential of ≈ 203 mV to reach a current density of 10 mA cm-2 in 1 M KOH, and a stability of 100 h at 1000 mA cm-2. Overall, this work provides a sacrificial Zn doping strategy to prepare highly efficient OER electrocatalysts. Display omitted
•A sacrificial Zn doping strategy was proposed to fabricate a self-supported NiFeZnP catalyst.•Zn as the sacrificial dopants promote the formation of the high-valence state of Ni sites.•In situ Raman demonstrates that Zn as the sacrificial dopants promote the formation of the NiFeOOH active phase.•Benefitting from the abundant exposed active sites, the NiFeZnP catalyst showed remarkable OER performances.
Exploitation of efficient and earth-abundant electrocatalysts for the oxygen evolution reaction (OER) is of great importance. Herein, we report that the formation of an amorphous Mn–Co–P shell on ...MnCo2O4 can boost its OER activity in alkaline media. The core–shell Mn–Co–P@MnCo2O4 nanowire array on Ti mesh (Mn–Co–P@MnCo2O4/Ti) shows excellent electrochemical catalytic activity and requires an overpotential of 269 mV to drive 10 mA cm−2 in 1.0 M KOH, which is 93 mV less than that for the MnCo2O4 nanoarray. Notably, this catalyst also shows strong long-term electrochemical durability with its activity being maintained for at least 100 h and achieves a high turnover frequency of 1.06 s−1 at an overpotential of 450 mV.
Developing efficient oxygen evolution reaction (OER) electrocatalysts is of great importance for sustainable energy conversion and storage. Ni-based catalysts have shown great potential as OER ...electrocatalysts, but their performance still needs to be improved. Herein, we report the multiple metal doped nickel nanoparticles synthesized via a simple oil phase strategy as efficient OER catalysts. The FeMnMoV–Ni exhibits superior OER performance with an overpotential of 220 mV at 10 mA cm−2 and a long-term stability of 250 h in 1 M KOH solution. In situ Raman analysis shows that the NiOOH site works as the active center and multiple metallic dopants facilitate the formation of NiOOH. Mo and V dopants promote the formation of high-valence state of Ni sites, and Mn dopants increase the electrochemical active surface area and expose more active sites. This work provides a novel strategy for catalyst design, which is critical for developing multiple metal doped catalysts.
Based on Fe doped Ni catalysts (Fe–Ni nanoparticles), we introduce multiple metal dopants using a simple oil phase strategy in this study. The Fe–Ni nanoparticles, with other 3 dopants of Mn, Mo, and V, show an overpotential of 220 mV at 10 mA cm−2. Display omitted
•Multiple metal doped catalysts were synthesized via a simple oil phase strategy.•Mo and V dopants promote the formation of high-valence state of Ni sites.•Mn dopants increase the electrochemical active surface area and expose more active sites.•Multiple metal dopants promote the formation of active sites NiOOH.
Tin halide perovskites are promising lead-free candidates for light-emitting diodes (LEDs), but their performance is hindered by the poor crystallinity quality and the oxidation of tin. It is ...necessary but challenging to simultaneously realize modulating crystallization, suppressing oxidation, and passivating defects to boost the device’s performance. Here, naphthol sulfonic salt is demonstrated as an effective multifunctional additive. The sulfonic group can retard crystallization by forming intermediate complexes with perovskite to form a pinhole-free film. The reducing hydroxyl group can prevent Sn2+ from oxidation and hinder the migration of I– ions. The high electron density of the naphthol ring can enhance the electrostatic attraction toward undercoordinated Sn2+ to passivate the defects. The synergistic effect of the multifunctional additive contributes to a boosted efficiency of 0.72% and a brightness of 132 cd m–2 for quantum-well structure phenethylammonium tin iodide ((PEA)2SnI4) LEDs, which represents the most effective lead-free perovskite LEDs in pure-red regions as far as we know.
To achieve the energy‐effective ammonia (NH3) production via the ambient‐condition electrochemical N2 reduction reaction (NRR), it is vital to ingeniously design an efficient electrocatalyst ...assembling the features of abundant surface deficiency, good dispersibility, high conductivity, and large surface specific area (SSA) via a simple way. Inspired by the fact that the MXene contains thermodynamically metastable marginal transition metal atoms, the oxygen‐vacancy‐rich TiO2 nanoparticles (NPs) in situ grown on the Ti3C2Tx nanosheets (TiO2/Ti3C2Tx) are prepared via a one‐step ethanol‐thermal treatment of the Ti3C2Tx MXene. The oxygen vacancies act as the main active sites for the NH3 synthesis. The highly conductive interior untreated Ti3C2Tx nanosheets could not only facilitate the electron transport but also avoid the self‐aggregation of the TiO2 NPs. Meanwhile, the TiO2 NPs generation could enhance the SSA of the Ti3C2Tx in return. Accordingly, the as‐prepared electrocatalyst exhibits an NH3 yield of 32.17 µg h−1 mg−1cat. at −0.55 V versus reversible hydrogen electrode (RHE) and a remarkable Faradaic efficiency of 16.07% at −0.45 V versus RHE in 0.1 m HCl, placing it as one of the most promising NRR electrocatalysts. Moreover, the density functional theory calculations confirm the lowest NRR energy barrier (0.40 eV) of TiO2 (101)/Ti3C2Tx compared with Ti3C2Tx or TiO2 (101) alone.
Oxygen‐vacancy‐rich TiO2 nanoparticles in situ grown on the MXene nanosheets (TiO2/Ti3C2Tx) are achieved via a one‐step ethanol‐thermal treatment of Ti3C2Tx MXene. Based on the synergistic effects of Ti3C2Tx and TiO2, TiO2/Ti3C2Tx exhibits much higher N2 reduction reaction (NRR) performance than that of the Ti3C2Tx or TiO2 alone. Density functional theory calculation is applied to confirm the NRR mechanism.
Thermal oxidation and hydrogen annealing were applied on a 100 μm thick Al-doped p-type 4H-SiC epitaxial wafer to modulate the minority carrier lifetime, which was investigated by microwave ...photoconductive decay (μ-PCD). The minority carrier lifetime decreased after each thermal oxidation. On the contrary, with the hydrogen annealing time increasing to 3 hours, the minority carrier lifetime increased from 1.1 μs (as-grown) to 3.14 μs and then saturated after the annealing time reached 4 hours. The increase of surface roughness from 0.236 nm to 0.316 nm may also be one of the reasons for limiting the further improvement of the minority carrier lifetimes. Moreover, the whole wafer mappings of minority carrier lifetimes before and after hydrogen annealing were measured and discussed. The average minority carrier lifetime was up to 1.94 μs and non-uniformity of carrier lifetime reached 38% after 4-hour hydrogen annealing. The increasing minority carrier lifetimes could be attributed to the double mechanisms of excess carbon atoms diffusion caused by selective etching of Si atoms and passivation of deep-level defects by hydrogen atoms.
Abstract
To achieve the energy‐effective ammonia (NH
3
) production via the ambient‐condition electrochemical N
2
reduction reaction (NRR), it is vital to ingeniously design an efficient ...electrocatalyst assembling the features of abundant surface deficiency, good dispersibility, high conductivity, and large surface specific area (SSA) via a simple way. Inspired by the fact that the MXene contains thermodynamically metastable marginal transition metal atoms, the oxygen‐vacancy‐rich TiO
2
nanoparticles (NPs) in situ grown on the Ti
3
C
2
T
x
nanosheets (TiO
2
/Ti
3
C
2
T
x
) are prepared via a one‐step ethanol‐thermal treatment of the Ti
3
C
2
T
x
MXene. The oxygen vacancies act as the main active sites for the NH
3
synthesis. The highly conductive interior untreated Ti
3
C
2
T
x
nanosheets could not only facilitate the electron transport but also avoid the self‐aggregation of the TiO
2
NPs. Meanwhile, the TiO
2
NPs generation could enhance the SSA of the Ti
3
C
2
T
x
in return. Accordingly, the as‐prepared electrocatalyst exhibits an NH
3
yield of 32.17 µg h
−1
mg
−1
cat.
at −0.55 V versus reversible hydrogen electrode (RHE) and a remarkable Faradaic efficiency of 16.07% at −0.45 V versus RHE in 0.1
m
HCl, placing it as one of the most promising NRR electrocatalysts. Moreover, the density functional theory calculations confirm the lowest NRR energy barrier (0.40 eV) of TiO
2
(101)/Ti
3
C
2
T
x
compared with Ti
3
C
2
T
x
or TiO
2
(101) alone.
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