CO₂ electroreduction to formate is technically feasible and economically viable, but still suffers from low selectivity and high overpotential at industrial current densities. Here, lattice-distorted metallic nanosheets with disorder-engineered metal sites are designed for industrial-current-density CO₂-to-formate conversion at low overpotentials. As a prototype, richly lattice-distorted bismuth nanosheets are first constructed, where abundant disorder-engineered Bi sites could be observed by high-angle annular dark-field scanning transmission electron microscopy image. In-situ Fourier-transform infrared spectra reveal the CO₂^•−* group is the key intermediate, while theoretical calculations suggest the electron-enriched Bi sites could effectively lower the CO₂ activation energy barrier by stabilizing the CO₂^•−* intermediate, further affirmed by the decreased formation energy from 0.49 to 0.39 eV. As a result, the richly lattice-distorted Bi nanosheets exhibit the ultrahigh current density of 800 mA·cm⁻² with 91% Faradaic efficiencies for CO₂-to-formate electroreduction, and the formate selectivity can reach nearly 100% at the current density of 200 mA·cm⁻² with a very low overpotential of ca. 570 mV, outperforming most reported metal-based electrocatalysts.

The major obstacle for selective CO₂ photoreduction to C₂ hydrocarbons lies in the difficulty of C–C coupling, which is usually restrained by the repulsive dipole–dipole interaction between adjacent carbonaceous intermediates. Herein, we first construct semiconducting atomic layers featuring abundant Metalⁿ⁺-Metal^δ+ pair sites (0 < δ < n), aiming to tailor asymmetric charge distribution on the carbonaceous intermediates and hence trigger their C–C coupling for selectively yielding C₂ hydrocarbons. As an example, we first fabricate Co-doped NiS₂ atomic layers possessing abundant Ni²⁺-Ni^δ+ (0 < δ < 2) pairs, where Co doping strategy can ensure higher amount of Ni ²⁺-Ni^δ+ pair sites. In-situ Fourier-transform infrared spectroscopy, quasi in-situ Raman spectroscopy and density-functional-theory calculations disclose the Ni²⁺-Ni^δ+ pair sites endow the adjacent CO intermediates with distinct charge densities, thus decreasing their dipole–dipole repulsion and hence lowering the rate-limiting C–C coupling reaction barrier. As a result, in simulated flue gas (10% CO₂ balance 90% N₂), the ethylene selectivity for Co-doped NiS₂ atomic layers reaches up to 74.3% with an activity of 70 μg·g⁻¹·h⁻¹, outperforming previously reported photocatalysts under similar operating conditions.

Sluggish separation and migration kinetics of the photogenerated carriers account for the low-efficiency of CO₂ photoreduction into CH₄. Design and construction two-dimensional (2D) in-plane heterostructures demonstrate to be an appealing approach to address above obstacles. Herein, we fabricate 2D in-plane heterostructured Ag₂S-In₂S₃ atomic layers via an ion-exchange strategy. Photoluminescence spectra, time-resolved photoluminescence spectra, and photoelectrochemical measurements firmly affirm the optimized carrier dynamics of the In₂S₃ atomic layers after the introduction of in-plane heterostructure. In-situ Fourier transform infrared spectroscopy spectra and density functional theory (DFT) calculations disclose the in-plane heterostructure contributes to CO₂ activation and modulates the adsorption strength of CO* intermediates to facilitate the formation of CHO* intermediates, which are further protonated to CH₄. In consequence, the in-plane heterostructure achieves the CH₄ evolution rate of 20 μmol·g^-1·h^-1, about 16.7 times higher than that of the In₂S₃ atomic layers. In short, this work proves construction of in-plane heterostructures as a promising method for obtaining high-efficiency CO₂-to-CH₄ photoconversion properties.

Photooxidation provides a promising strategy for removing the dominant indoor pollutant of HCHO, while the underlying photooxidation mechanism is still unclear, especially the exact role of H₂O molecules. Herein, we utilize in-situ spectral techniques to unveil the H₂O-mediated HCHO photooxidation mechanism. As an example, the synthetic defective Bi₂WO₆ ultrathin sheets realize high-rate HCHO photooxidation with the assistance of H₂O at room temperature. In-situ electron paramagnetic resonance spectroscopy demonstrates the existence of •OH radicals, possibly stemmed from H₂O oxidation by the photoexcited holes. Synchrotron-radiation vacuum ultraviolet photoionization mass spectroscopy and H₂¹⁸O isotope-labeling experiment directly evidence the formed •OH radicals as the source of oxygen atoms, trigger HCHO photooxidation to produce CO₂, while in-situ Fourier transform infrared spectroscopy discloses the HCOO* radical is the main photooxidation intermediate. Density-functional-theory calculations further reveal the •OH formation process is the rate-limiting step, strongly verifying the critical role of H₂O in promoting HCHO photooxidation. This work first clearly uncovers the H₂O-mediated HCHO photooxidation mechanism, holding promise for high-efficiency indoor HCHO removal at ambient conditions.

Regulating the selectivity of CO₂ photoreduction is particularly challenging. Herein, we propose ideal models of atomic layers with/without element doping to investigate the effect of doping engineering to tune the selectivity of CO₂ photoreduction. Prototypical ZnCo₂O₄ atomic layers with/without Ni-doping were first synthesized. Density functional theory calculations reveal that introducing Ni atoms creates several new energy levels and increases the density-of-states at the conduction band minimum. Synchrotron radiation photoemission spectroscopy demonstrates that the band structures are suitable for CO₂ photoreduction, while the surface photovoltage spectra demonstrate that Ni doping increases the carrier separation efficiency. In situ diffuse reflectance Fourier transform infrared spectra disclose that the CO₂^·- radical is the main intermediate, while temperature-programed desorption curves reveal that the ZnCo₂O₄ atomic layers with/without Ni doping favor the respective CO and CH₄ desorption. The Ni-doped ZnCo₂O₄ atomic layers exhibit a 3.5-time higher CO selectivity than the ZnCo₂O₄ atomic layers. This work establishes a clear correlation between elemental doping and selectivity regulation for CO₂ photoreduction, opening new possibilities for tailoring solar-driven photocatalytic behaviors.