Selenium (Se), as an important quasi-metal element, has attracted much attention in the fields of thin-film solar cells, electrocatalysts and energy storage applications, due to its unique physical and chemical properties. However, the electrochemical behavior of Se in different systems from electrolytic cell to battery are complex and not fully understood. In this article, we focus on the electrochemical processes of Se in aqueous solutions, molten salts and ionic liquid electrolytes, as well as the application of Se-containing materials in energy storage. Initially, the electrochemical behaviors of Se-containing species in different systems are comprehensively summarized to understand the complexity of the kinetic processes and guide the Se electrodeposition. Then, the relationship between the deposition conditions and resulting structure and morphology of electrodeposited Se is discussed, so as to regulate the morphology and composition of the products. Finally, the advanced energy storage applications of Se in thin-film solar cells and secondary batteries are reviewed, and the electrochemical reaction processes of Se are systematically comprehended in monovalent and multivalent metal-ion batteries. Based on understanding the fundamental electrochemistry mechanism, the future development directions of Se-containing materials are considered in view of the in-depth review of reaction kinetics and energy storage applications.

In this work, we open an avenue toward rational design of potential efficient catalysts for sustainable ammonia synthesis through composition engineering strategy by exploiting the synergistic effects among the active sites as exemplified by diatomic metals anchored graphdiyne via the combination of hierarchical high-throughput screening, first-principles calculations, and molecular dynamics simulations. Totally 43 highly efficient catalysts feature ultralow onset potentials (|U_onset| ≤ 0.40 V) with Rh-Hf and Rh-Ta showing negligible onset potentials of 0 and -0.04 V, respectively. Extremely high catalytic activities of Rh-Hf and Rh-Ta can be ascribed to the synergistic effects. When forming heteronuclears, the combinations of relatively weak (such as Rh) and relatively strong (such as Hf or Ta) components usually lead to the optimal strengths of adsorption Gibbs free energies of reaction intermediates. The origin can be ascribed to the mediate d-band centers of Rh-Hf and Rh-Ta, which lead to the optimal adsorption strengths of intermediates, thereby bringing the high catalytic activities. Our work provides a new and general strategy toward the architecture of highly efficient catalysts not only for electrocatalytic nitrogen reduction reaction (eNRR) but also for other important reactions. We expect that our work will boost both experimental and theoretical efforts in this direction.

To demonstrate flexible and tandem device applications, a low-temperature Cu₂ZnSnSe₄ (CZTSe) deposition process, combined with efficient alkali doping, was developed. First, high-quality CZTSe films were grown at 480 ℃ by a single co-evaporation, which is applicable to polyimide (PI) substrate. Because of the alkali-free substrate, Na and K alkali doping were systematically studied and optimized to precisely control the alkali distribution in CZTSe. The bulk defect density was significantly reduced by suppression of deep acceptor states after the (NaF + KF) PDTs. Through the low-temperature deposition with (NaF + KF) PDTs, the CZTSe device on glass yields the best efficiency of 8.1% with an improved V_OC deficit of 646 mV. The developed deposition technologies have been applied to PI. For the first time, we report the highest efficiency of 6.92% for flexible CZTSe solar cells on PI. Additionally, CZTSe devices were utilized as bottom cells to fabricate four-terminal CZTSe/perovskite tandem cells because of a low bandgap of CZTSe (~1.0 eV) so that the tandem cell yielded an efficiency of 20%. The obtained results show that CZTSe solar cells prepared by a low-temperature process with in-situ alkali doping can be utilized for flexible thin-film solar cells as well as tandem device applications.