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Seeking efficient, stable, and inexpensive electrocatalysts applied to water splitting and fuel cells in acidic media is still challenging for the development of renewable energy. Herein, we propose a single atom catalyst based on heterojunction composed of Pd–C4N and XMoY (X, Y = S, Se, Te), and conduct a detailed exploration of its oxygen reduction reaction (ORR), oxygen reduction reaction (OER), and hydrogen evolution reaction (HER) catalytic performance using density functional theory methods. First, all Pd–C4N/XMoY is proven to have good stability by calculating binding energy. Then, the ORR/OER electrocatalytic behavior of Pd–C4N/XMoY is investigated, and the potential-determining step of most catalysts for ORR is *OH reduction, while for the OER, it is *OH to *O. Additionally, all catalysts exhibit good catalytic activity for the ORR/OER, but only five have better catalytic activity than Pt(111). In particular, Pd–C4N/SMoSe exhibits a negligible potential barrier for the HER (−0.004 V). Pd–C4N/SeMoTe presents immense trifunctional activities toward ORR/OER/HER with overpotentials of 0.32/0.28/–0.02 V. The electronic structure analysis proves that the high activity is attributed to the good conductivity of the material itself and the adjustable binding ability of the *OH. Our report contributes to comprehending and designing more efficient single-atom catalysts to meet the demand for multifunctional catalysts. [ABSTRACT FROM AUTHOR]

The electromagnetic pollution problem is becoming increasingly serious due to the speedy advance of electronic communication devices. There are broad application prospects for the development of flexible, wearable composite films with high electromagnetic interference (EMI)-shielding performance. The MX@AC composite films were prepared from MXene, silver nanowires (AgNWs) and cellulose nanocrystals (CNCs) with a sandwich structure. Benefiting from the upper and lower frame structure formed by winding 1D AgNWs and CNC, the tensile strength of the MX@AC was improved to 35 MPa (12.5 wt% CNC content) from 4 MPa (0 wt% CNC content). The high conductivity of MXene and AgNWs resulted in the MX@AC composite film conductivity up to 90,670 S/m, EMI SE for 90 dB, as well as SSE/t up to 7797 dB cm2 g−1. And the MX@AC composite film was tested for practical application, showing that it can effectively isolate electromagnetic waves in practical application. [ABSTRACT FROM AUTHOR]

Finding efficient and stable electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is imperative for advancing zinc-air batteries. Herein, the effect of transition metal anchored on Nb 2 CO 2 with different N content to form TM-N x -Nb 2 CO 2 on the catalytic activity of ORR and OER is investigated by density functional theory. Among all the designed TM-N x -Nb 2 CO 2 , Pt-N 12.50% -Nb 2 CO 2 , Pt-N 37.50% -Nb 2 CO 2 , Pt-N 50.00% -Nb 2 CO 2 , Pd-N 68.75% -Nb 2 CO 2 , and Pd-N 100% -Nb 2 CO 2 are excellent ORR electrocatalysts with η ORR values of 0.38, 0.36, 0.38, 0.38, and 0.34 V, respectively. Rh-Nb 2 CO 2 , Rh-N 12.50% -Nb 2 CO 2 , Rh-N 31.25% -Nb 2 CO 2 , Rh-N 37.50% -Nb 2 CO 2 , Rh-N 50.00% -Nb 2 CO 2 , Pt-N 50.00% -Nb 2 CO 2 , Rh-N 68.75% -Nb 2 CO 2 , and Rh-N 81.25% -Nb 2 CO 2 are excellent OER electrocatalysts with η OER values of 0.33, 0.37, 0.34, 0.36, 0.37, 0.34, 0.38, and 0.33 V, respectively. Notably, Rh-Nb 2 CO 2 and Pt-N 50.00% -Nb 2 CO 2 exhibit outstanding ORR and OER bifunctional catalytic activity with potential gap values of 0.80 and 0.72 V, respectively, which are higher than the activities of most reported bifunctional catalysts. Furthermore, electronic structure analysis indicates that the moderate adsorption strength of oxygen-containing intermediates on active centers is crucial for achieving highly active bifunctional catalysts for ORR and OER. This study provides a strategy for the design of novel ORR and OER catalysts using 2D MXene materials.