carbon dioxide reduction, which can also be driven by clean and renewable energies such as wind, solar and hydropower resources, represent crucial steps of these renewable energy devices. However, the performances of these chemical reactions strongly rely on the energy storage and conversion efficiencies of the catalytic materials deposited on the electrodes. [6][7][8][9][10] Therefore, the development of robust and earth-abundant catalysts with both high catalytic activity and selectivity play a critical role in the real application of these devices.Current catalysts for energy-related chemical reactions are heavily dependent on noble metals, which impedes their large potential commercialization. [11][12][13] Further, the catalytic process mostly occurred on the metal surfaces, leading to the very low utilization efficiency of the catalysts. To minimize the waste of the non-accessible atoms in the bulk metals, researchers developed several strategies to modify metal structures in order to expose as many metal atoms as possible. [10,[14][15][16][17][18] One of the most popular methods is to downsize the solid metal catalysts to the atomic level (Figure 1). More interestingly, the catalytic behaviors of the metal catalysts with different sizes have significantly Atomic catalysts (AC) are gaining extensive research interest as the most active new frontier in heterogeneous catalysis due to their unique electronic structures and maximum atom-utilization efficiencies. Among all the atom catalysts, atomically dispersed heteronuclear dual-atom catalysts (HDACs), which are featured with asymmetric active sites, have recently opened new pathways in the field of advancing atomic catalysis. In this review, the up-todate investigations on heteronuclear dual-atom catalysts together with the last advances on their theoretical predictions and experimental constructions are summarized. Furthermore, the current experimental synthetic strategies and accessible characterization techniques for these kinds of atomic catalysts, are also discussed. Finally, the crucial challenges in both theoretical and experimental aspects, as well as the future prospects of HDACs for energy-related applications are provided. It is believed that this review will inspire the rational design and synthesis of the new generation of highly effective HDACs.

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Ferroelectrics is expected to be an alternative to traditional solar cells, because its bulk photovoltaic effect (BPVE) may overcome the Shockley–Queisser limit. Here, we propose that a family of polar materials without centrosymmetry, distorted 1T (1T′′′) transition-metal dichalcogenides, shows a large BPVE in the infrared and visible light due to their moderate band gaps based on density-functional-theory (DFT) calculations. We find that the BPVEs in bulks are much higher than those in monolayers because of the smaller band gaps and more delocalized valence band states. We further show that strain engineering serves as an efficient strategy to enhance the BPVE of 1T′′′-MoS2 bulk. The shift-current responses in the bulks spotlight their potential for applications into solar energy harvesting. This work provides the theoretical evidence of BPVE in 1T′′′ transition-metal dichalcogenides and guidance on the design of novel materials with an enhanced BPVE for green-energy technologies.

Massively converting nitrogen gas to ammonia is a key process in modern agricultural and industrial fields. The conventional Haber–Bosch process for NH3 production has to be carried out under extreme conditions, leading to high energy consumption and huge emission of greenhouse gases. Electrochemical N2 reduction is a promising way for NH3 production due to its sustainable process and feasibility in an ambient environment. In this work, we screen the transition metals (TM), including 26 elements, supported on two-dimensional (2D) Nb2CN2 (TM-Nb2CN2) for their applications in the electrochemical reduction of N2 (NRR) based on first-principles calculations. We show that most SACs can bind with Nb2CN2 strongly through a TM-3N configuration. We find that Mn-Nb2CN2 is a promising candidate for the N2 reduction reaction (NRR), with a low overpotential of 0.51 V through the distal mechanism. Importantly, TM-Nb2CN2 presents high selectivity to NRR by blocking the hydrogen adsorption and preventing the hydrogen evolution reaction. Moreover, the scaling relationship and Bader charge analysis provide an insightful understanding of the mechanism for NRR on single-atom catalysts (SACs) anchored on 2D MXenes. Our findings may guide the design of novel substrates for SACs with effectively improved performance.

Among all the 2D-carbon materials, graphyne is currently one of the most interesting carbon allotropes besides graphene. It has potential applications in a wide variety of scientific fields owed to...