Local environment plays an important role in steering the reaction pathways in electrochemical CO 2 reduction reaction. Here, we present three approaches to modulate local CO 2 concentration in gas-diffusion electrode flow electrolyzers. Employing monodisperse Cu 2 O nanoparticles as the model catalysts, we demonstrate that providing a moderate local CO 2 concentration is effective in promoting C-C coupling. Ultimately, this study serves as a rational guide to tune CO 2 mass transport in gas-diffusion electrode electrolyzers for the optimal production of valuable multi-carbon molecules.

Development of efficient and selective electrocatalysts is a key challenge to achieve an industry-relevant electrochemical CO 2 reduction reaction (CO 2 RR) to produce commodity chemicals. Here, we report that Au 25 clusters with Authiolate staple motifs can initiate electrocatalytic reduction of CO 2 to CO with nearly zero energy loss and achieve a high CO 2 RR current density of 540 mA cm −2 in a gas-phase reactor. Electrochemical kinetic investigations revealed that the high CO 2 RR activity of the Au 25 originates from the strong CO 2 binding affinity, leading to high CO 2 electrolysis performance in both concentrated and dilute CO 2 streams. Finally, we demonstrated an 18.0% solar-to-CO conversion efficiency using a Au 25 electrolyzer powered by a Ga 0.5 In 0.5 P/GaAs photovoltaic cell. The electrolyzer also showed 15.9% efficiency and a 5.2% solar-driven single-path CO 2 conversion rate in a 10% CO 2 gas stream, the CO 2 concentration in a typical flue gas.

Satellites carrying sources of entangled photons could establish a global quantum network, enabling private encryption keys between any two points on Earth. Despite numerous proposals, demonstration of space-based quantum systems has been limited due to the cost of traditional satellites. We are using very small spacecraft to accelerate progress. We report the in-orbit operation of a photon pair source aboard a 1.65 kg nanosatellite and demonstrate pair generation and polarization correlation under space conditions. The in-orbit photon correlations exhibit a contrast of 97 ± 2%, matching ground-based tests. This pathfinding mission overcomes the challenge of demonstrating in-orbit performance for the components of future entangled photon experiments. Ongoing operation establishes the in-orbit lifetime of these critical components. More generally, this demonstrates the ability for nanosatellites to enable faster progress in space-based research.Progress in quantum computers and their threat to public key cryptography is driving new forms of encryption [1]. One promising alternative is quantum key distribution (QKD) which provides provable security underpinned by quantum physics [2]. In particular, QKD can be achieved using pairs of photons that possess fundamental correlations known as quantum entanglement [3]. Practically, entanglement-based QKD enables a reduction in the number of trusted components [4]. A global quantum network for distributing entangled photon pairs will enable strong encryption keys to be shared between any two points on Earth.Entanglement-based QKD is a mature technology [5][6][7] compared with other entanglement-assisted applications. However, it shares a common range limit with more conventional prepare-send-measure QKD schemes [8]. Metropolitan scale QKD networks are possible using optical fiber or free-space links, but fiber losses and ground-level atmospheric turbulence preclude extending these networks to a global scale. Quantum repeater technology that can overcome these losses is still in the starting stages of being researched [9].Scalable global entanglement distribution can be achieved using a constellation of satellites equipped with spaceto-ground optical links [10]. The technology behind these links are relatively well-documented (e.g. [11][12][13]). Most proposals [14] employ a downlink to minimize transmission loss [15]. A source of photon pairs is placed on board a satellite in Earth orbit that will then either act as a trusted relay between two ground nodes, or beam one photon to one ground station and its pair photon to a different ground station. An additional advantage of space-based entanglement systems is that they allow fundamental tests of the possible overlap between quantum and relativistic regimes for which operation in space is necessary [16].Despite many preliminary studies on space quantum systems [11,12,15,[17][18][19][20][21] there has been limited published work demonstrating relevant technology in space [12,21] due to the prohibitive cost of traditional sp...

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