The photoelectrochemical carbon dioxide reduction reaction (PEC-CO 2 RR) allows us to convert solar power to chemical energy with photosensitive materials. Semiconductor-based, plasmon-assisted, and dye-sensitized systems have been extensively investigated in the PEC-CO 2 RR. Beyond the remarkable progress in materials science, it is expected to realize new systems for satisfying the needs of both research discoveries and industry applications. In this Perspective, we summarize the latest progress in the field of the PEC-CO 2 RR, focusing on enhancing efficiencies via matching photoelectron flux, charge transfer rate, and mass transport rate. Based on the principles for the state-of-the-art PEC-CO 2 RR, new designs of the system engineering strategies on photoelectrode fabrication, reactor design, electrolyte optimization, and membrane selection are proposed to enhance selectivity and stability of the PEC-CO 2 RR.

A Si/ZnO/Cu2O p‐n‐p heterojunction potential well with electron tunnels is fabricated for selective photoelectrochemical CO2 reduction to ethanol. This heterojunction is formed by growing n‐type ZnO nanosheets between defect‐rich p‐type Cu2O nanoparticles and nanoporous p‐type Si. Due to the existence of this potential well, the photogenerated electrons are trapped and accumulate inside n‐ZnO at low biases with the assistance of a ≈0.6 V built‐in potential, and escape into the Cu2O defect band. Under simulated sunlight, the Si/ZnO/Cu2O photocathode exhibits an onset potential of 0.2 V versus reversible hydrogen electrode (RHE) for aqueous photoelectrochemical CO2 reduction. Due to the confined electron energy in tunneling, the product selectivity is substantially tuned from CO or formate to ethanol, with an excellent Faradaic efficiency of ethanol over 60% at 0 V versus RHE.

Melatonin-loaded liposomes (MLL) were successfully prepared using rapid expansion of supercritical solution technology. The effects of supercritical pressure on encapsulation efficiency (EE) and average particle size were then analysed. Meanwhile, temperature, formation time and ethanol concentration in the products were studied and optimised based on the response surface methodology (RSM). An in vitro simulated digestion model was also established to evaluate the release performance of MLL. The results showed that 140 bar was the best pressure for maximising the EE value using RSM optimisation, reaching up to 82.2%. MLL characterisations were performed using analytic techniques including infrared spectroscopy, transmission electron microscopy, a laser scattering particle size analyser and gas chromatograph-mass spectrometer. The size distribution was uniform, with an average diameter of 66 nm. Stability tests proved that MLL maintained good preservation duration, and residual solvent experiments indicated that only 1.03% (mass ratio) of ethanol remained in the products. Simulated release experiments indicated the slow release feature in early digestive stages and more thorough characteristics in later stages of simulated digestion.

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Photocatalytic CO2 conversion into high-value chemicals has been emerging as an attractive research direction in achieving carbon resource sustainability. The chemical products can be categorized into C1 and multi-carbon (C2+)...