MoO3 nanosheets act as an efficient electrocatalyst for N2 fixation to NH3 with excellent selectivity at ambient conditions. In 0.1 M HCl, they show high 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%.
Efficient
and low-cost electrocatalysts for oxygen evolution reaction
(OER), particularly in neutral conditions, are of significant importance
for renewable energy technologies such as CO2 reduction
and seawater splitting electrolysis. High-valent transition-metal
sites have been considered as OER active sites; however, the rational
design and construction of these sites remain a big challenge. Here,
we report a trimetallic NiFeCu oxyhydroxide electrocatalyst, in which
high-valent Ni sites are promoted and stabilized by the atomically
embedded Cu, as evidenced by X-ray photoelectron spectroscopy and
X-ray absorption spectroscopy. Through compositional optimization,
Ni6Fe1Cu1 catalysts achieved an overpotential
of 385 mV at 10 mA cm–2, a Tafel slope of 164 mV
dec–1, and a stability of 100 h at pH = 7.2. Density
function theory calculations demonstrated that the Cu-doping facilitates
the formation of high-valent Ni and thus promotes OER electrocatalysis
through modulating the d-band center of Ni and reducing the adsorption
energy of oxygenated intermediates on the surface of the catalyst.
This work paves a promising avenue for the construction of desired
high-valent metal OER catalysts by embedding redox inactive metals.
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.
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