The increasingly stringent requirement in large‐scale energy storage necessitates the development of high‐performance sodium‐ion batteries (SIBs) that can operate under low‐temperature (LT) ...environment. Although SIBs can achieve good cycling stability and rate performance at room temperature, the sluggish electrochemical reaction kinetics at low temperature remains a great challenge for SIBs. Here, a superior LT SIB composed of 3D porous Na3V2(PO4)3/C (NVP/C‐F) and NaTi2(PO4)3/C foams (NTP/C‐F) is developed. First‐principles calculations reveal that the intrinsic Na+ diffusivity in NASICON‐type NVP and NTP is extremely high (maximum 3.84 × 10−5 for NVP and 2.94 × 10−9 cm2 s−1 for NTP) at –20 °C. In addition, the designed 3D interconnected porous foam structures demonstrate excellent electrolyte absorption ability and Na+ transport performance at low temperature. As a result, under −20 °C, the NVP/CF and NTP/CF electrodes (half‐cell configuration) can attain reversible capacities close to their theoretical values, and are able to be charged and discharged rapidly (20 C) for 1000 cycles. Based on these features, the designed NTP/CF||NVP/CF full cell also displays superb LT kinetics and cycling stability, making a great stride forward in the development of LT SIBs.
A high‐performance low‐temperature sodium ion full battery composed of 3D porous Na3V2(PO4)3/C and NaTi2(PO4)3/C foams is developed. Owing to the fast Na+ diffusivity of these two NASICON‐type electrodes and excellent electrolyte absorption ability of the foam structure, this full battery demonstrates superb kinetics and cycling stability (e.g., 20 C over 1000 cycles) at −20 °C.
Identifying the nature of active centers and structure–performance correlations is of fundamental importance for the successful design of more energy-efficient and/or selective catalysts. Recently, ...the studies of metal-free catalysts containing sp2- or sp3-hybridized B sites have displayed an attractive prospect for N2 reduction but have obscured the nature of the optimal active B species. Herein, with the aid of first-principles calculations, we explicitly disclose that sp2-hybridized B is the optimal species for providing high activity for N2 reduction and particularly outstanding capability to suppress the competing hydrogen evolution reaction. Specifically, the system with B substituting an edge N atom in the cavity of C2N is proposed to be highly promising for N2 reduction under mild conditions. The developed comprehensive insight is of clear significance for the rational design of advanced catalysts for NH3 synthesis under mild conditions.
Piezo‐electrocatalysis as an emerging mechano‐to‐chemistry energy conversion technique opens multiple innovative opportunities and draws great interest over the past decade. However, the two ...potential mechanisms in piezo‐electrocatalysis, i.e., screening charge effect and energy band theory, generally coexist in the most piezoelectrics, making the essential mechanism remain controversial. Here, for the first time, the two mechanisms in piezo‐electrocatalytic CO2 reduction reaction (PECRR) is distinguished through a narrow‐bandgap piezo‐electrocatalyst strategy using MoS2 nanoflakes as demo. With conduction band of −0.12 eV, the MoS2 nanoflakes are unsatisfied for CO2‐to‐CO redox potential of −0.53 eV, yet they achieve an ultrahigh CO yield of ≈543.1 µmol g−1 h−1 in PECRR. Potential band position shifts under vibration are still unsatisfied with CO2‐to‐CO potential verified by theoretical investigation and piezo‐photocatalytic experiment, further indicating that the mechanism of piezo‐electrocatalysis is independent of band position. Besides, MoS2 nanoflakes exhibit unexpected intense “breathing” effect under vibration and enable the naked‐eye‐visible inhalation of CO2 gas, independently achieving the complete carbon cycle chain from CO2 capture to conversion. The CO2 inhalation and conversion processes in PECRR are revealed by a self‐designed in situ reaction cell. This work brings new insights into the essential mechanism and surface reaction evolution of piezo‐electrocatalysis.
Piezo‐electrocatalysis as an emerging mechano‐to‐chemistry energy conversion technique opens multiple innovative opportunities, drawing great interest but also suffering from the controversial mechanisms. A narrow‐bandgap piezo‐electrocatalyst strategy is proposed by choosing CO2 reduction as a probe reaction to distinguish the two potential mechanisms, i.e., screening charge effect and energy band theory, and reveal that piezo‐electrocatalysis is independent of band positions.
We use first-principles calculations to systematically explore the potential of transition metal atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) embedded in buckled ...monolayer g-C
3
N
4
as single-atom catalysts. We show that clustering of Sc and Ti on g-C
3
N
4
is thermodynamically impeded and that V, Cr, Mn, and Cu are much less susceptible to clustering than the other TM atoms under investigation. Strong bonding of the transition metal atoms in the cavities of g-C
3
N
4
and high diffusion barriers together are responsible for single-atom fixation. Analysis of the CO oxidation process indicates that embedding of Cr and Mn in g-C
3
N
4
gives rise to promising single-atom catalysts at low temperature.
We use first-principles calculations to systematically explore the potential of transition metal atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Ir, Pt, and Au) embedded in buckled monolayer g-C
3
N
4
as single-atom catalysts.
Solar-driven overall water splitting is highly desirable for hydrogen generation with sustainable energy sources, which need efficient, earth-abundant, robust, and bifunctional electrocatalysts for ...both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, we propose a heterogeneous bimetallic phosphide/sulfide nanocomposite electrocatalyst of NiFeSP on nickel foam (NiFeSP/NF), which shows superior electrocatalytic activity of low overpotentials of 91 mV at −10 mA cm–2 for HER and of 240 mV at 50 mA cm–2 for OER in 1 M KOH solution. In addition, the NiFeSP/NF presents excellent overall water splitting performance with a cell voltage as low as 1.58 V at a current density of 10 mA cm–2. Combining with a photovoltaic device of a Si solar cell or integrating into photoelectrochemical (PEC) systems, the bifunctional NiFeSP/NF electrocatalyst implements unassisted solar-driven water splitting with a solar-to-hydrogen conversion efficiency of ∼9.2% and significantly enhanced PEC performance, respectively.
High-valence cobalt sites are considered as highly active centers for the oxygen evolution reaction (OER) and their corresponding construction is thus of primary importance in the pursuit of ...outstanding performance. Herein, we report the design and facile synthesis of abundant high-valence cobalt sites by introducing Zn
2+
into CoFe Prussian blue analogues (PBAs). The modification results in the drastic morphological transformation from a pure phase (CoFe-PBA) to a three-phase composite (CoFeZn-PBA), with a significant increase not only the amount of highly oxidized Co sites but the specific surface area (by up to 4 times). Moreover, the obtained sample also exhibits outstanding electric conductivity. Consequently, an excellent OER performance with an overpotential of 343 mV@10 mA cm
−2
and a Tafel slope of 75 mV dec
−1
was achieved in CoFeZn-PBA, which outperforms the commercial IrO
2
catalyst. Further analysis reveals that CoFeZn-PBA becomes (oxyhydr)oxides after the OER.
Upon the introduction of Zn
2+
, the sample transforms from a pure phase (CoFe-PBA) to a three-phase composite (CoFeZn-PBA), leading to a sharply increased Co
3+
/Co
2+
ratio and an outstanding OER performance.
Platinum (Pt) is well-known as the best-performing catalyst for the hydrogen evolution reaction (HER), but its practical application is severely hindered by its prohibitively high cost and ...problematic performance in alkaline electrolyte. Herein, we report that the issues of intrinsic activity and cost concern of Pt can be simultaneously addressed by employing a combination of concerted catalysis and nanoengineering strategies. Motivated by our density functional theory (DFT) calculations that the cooperative catalysis between Pt and NiO would lead to a better HER activity in comparison to Pt solely in alkaline solution, we successfully synthesized a Pt/NiO@Ni/NF nanocomposite catalyst by depositing highly dispersed Pt nanoclusters/nanoparticles on a honeycomb-like NiO@Ni film supported on Ni foam (NF). The resulting Pt/NiO@Ni/NF catalyst outperforms the commercial Pt/C catalyst with a high and stable HER activity in alkaline solution and, more impressively, with an economical Pt content as low as ∼0.1 mg cm–2.
Developing transition metal dichalcogenides as electrocatalysts has attracted great interest due to their tunable electronic properties and good thermal stabilities. Herein, we propose a PdTe2 ...bilayer as a promising electrocatalyst candidate towards the oxygen reduction reaction (ORR), based on extensive investigation of the electronic properties of PdTe2 thin films as well as atomic-level reaction kinetics at explicit electrode potentials. We verify that under electrochemical reducing conditions, the electron emerging on the electrode surface is directly transferred to O2 adsorbed on the PdTe2 bilayer, which greatly reduces the dissociation barrier of O2, and thereby facilitates the ORR to proceed via a dissociative pathway. Moreover, the barriers of the electrochemical steps in this pathway are all found to be less than 0.1 eV at the ORR limiting potential, demonstrating fast ORR kinetics at ambient conditions. This unique mechanism offers excellent energy efficiency and four-electron selectivity for the PdTe2 bilayer, and it is identified as a promising candidate for fuel cell applications.
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•The − C≡C − of graphyne can stabilize single TM atoms to form SACs without N dopants.•Several promising candidates were provided for bifunctional ORR/OER.•A full picture for ...efficiently screening bifunctional SACs was established via a robust and handy intrinsic descriptor.•A general model was given to describe the interaction between TM and OH.
Noble metals are well-known to be highly efficient for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, their scarcity and high price have severely hampered their large-scale commercial applications. In this work, with the aid of density functional theory calculations we systematically screened 26 types of transition metal atom embedded γ-graphyne monolayer (TM-GY) as potential effective and cheap single functional and bifunctional single-atom catalysts (SACs) for ORR/OER. The catalytic activity of ORR/OER can be expressed by a single descriptor of the adsorption free energy of the OH intermediate. Our research shows that Fe, Ir, Co, Rh, Cu, Ni, Pd and Pt-GY are potential single-functional and bifunctional SACs candidates for ORR or/and OER. Specifically, Co-GY was found to be the optimal bifunctional SAC for ORR and OER. A three-step strategy for screening bifunctional SACs was put forward: (i) non-radioactive/toxic element, (ii) single-function SACs and (iii) bifunctional SACs.
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