The development of efficient electrocatalysts for the CO 2 reduction reaction (CO 2 RR) remains ac hallenge.D emonstrated here is aN iSn atomic-pair electrocatalyst (NiSn-APC) on ah ierarchical integrated electrode,w hich exhibits as ynergistic effect in simultaneously promoting the activity and selectivity of the CO 2 RR to formate.The NiSn atomic pair consists of adjacent Ni and Sn, eachc oordinated with four nitrogen atoms (N 4-Ni-Sn-N 4). The as-prepared NiSn-APC displays exceptional activity for the CO 2 RR to formate with at urnover frequency of 4752 h À1 ,aformate productivity of 36.7 mol h À1 g Sn À1 and an utilization degree of active sites (57.9 %), which are superior to previously reported singleatomic catalysts.B oth experimental data and density-functional theory calculations verify the electron redistribution of Sn imposed by adjacent Ni, which reduces the energy barrier of the *OCHO intermediate and makes this potential-determining step thermodynamically spontaneous.This synergistic catalysis provides as uccessful paradigm for rational design and preparation of atomic-pair electrocatalysts with enhanced performance.
Single‐atomic electrocatalysts (SACs) have shown great promise in electrocatalysis fields owing to their theoretical maximum atom utilization (100%). Yet still, it is far from expectation in practical applications due to entrapping within supports and blocking by aggregation. Herein, self‐supported carbon nanosheet arrays consisting of single‐atomic Co electrocatalyst (SS‐Co‐SAC) toward oxygen‐involved reaction and zinc–air batteries are reported. Impressively, the as‐synthesized SS‐Co‐SAC gives a markedly enhanced utilization of active sites (≈22.3%@2.3 wt%) as a result of single‐atomic dispersion of Co within a unique nanosheet arrays architecture, which is the largest value among other reported results. Benefiting from the high utilization of active sites, the SS‐Co‐SAC electrode exhibits outstanding electrocatalytic performance for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Notably, the turnover frequency value for ORR is determined to be ≈9.26 s−1, which stands for the highest level among noble metal‐free electrocatalysts reported previously. Moreover, as an air‐cathode for zinc–air batteries with SS‐Co‐SAC, a power density of 195.1 mW cm−2 and a robust durability are achieved. It is believed that this study would guide the future design of highly active and durable single‐atom catalysts for both fundamental research and practical applications.
The
development of low-cost adsorbent with excellent adsorption
property remains a big challenge. Herein, the functionalization of
natural peach gum polysaccharide (PGP) with multiple amine groups
for the removal of toxic Cr(VI) ions from water was studied. The obtained
PGP-NH
2
gel exhibited high-removal efficiency (>99.5%)
toward Cr(VI) ions, especially with relatively low initial concentration
of Cr(VI) ions (≤250 mg/L). The influences of pH, ionic strength,
contact time, initial concentration, and temperature on the adsorption
of Cr(VI) ions were systematically investigated. The PGP-NH
2
gel showed rapid adsorption rate and could reach adsorption equilibrium
within about 40 min. The Cr(VI) ion uptake process could be described
by pseudo-second-order kinetic and Langmuir isotherm models. The maximum
adsorption capacity of PGP-NH
2
gel could reach 188.32 mg/g.
Thermodynamic investigation results indicated the spontaneous and
exothermic characteristic of the uptake process. Moreover, the PGP-NH
2
gel also exhibited favorable reusability, and 135.52 mg/g
of adsorption capacity was retained even after being reused for five
times. Considering its low cost and superior uptake property, the
PGP-NH
2
gel holds a great promise for employing as an adsorbent
to treat Cr(VI) ion-containing wastewater.
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