Defects can greatly influence the properties of oxide materials; however, facile defect engineering of oxides at room temperature remains challenging. The generation of defects in oxides is difficult to control by conventional chemical reduction methods that usually require high temperatures and are time consuming. Here, we develop a facile room-temperature lithium reduction strategy to implant defects into a series of oxide nanoparticles including titanium dioxide (TiO₂), zinc oxide (ZnO), tin dioxide (SnO₂), and cerium dioxide (CeO₂). Our lithium reduction strategy shows advantages including all-room-temperature processing, controllability, time efficiency, versatility and scalability. As a potential application, the photocatalytic hydrogen evolution performance of defective TiO₂ is examined. The hydrogen evolution rate increases up to 41.8 mmol g⁻¹ h⁻¹ under one solar light irradiation, which is ~3 times higher than that of the pristine nanoparticles. The strategy of tuning defect oxides used in this work may be beneficial for many other related applications.

Photochemical solution-phase reactions have been widely applied for the syntheses of nanocrystals. In particular, tuning of the nucleation and growth of solids has been a major area of focus. Here we demonstrate a facile approach to generate atomically dispersed platinum via photochemical reduction of frozen chloroplatinic acid solution using ultraviolet light. Using this iced-photochemical reduction, the aggregation of atoms is prevented, and single atoms are successfully stabilized. The platinum atoms are deposited on various substrates, including mesoporous carbon, graphene, carbon nanotubes, titanium dioxide nanoparticles, and zinc oxide nanowires. The atomically dispersed platinum on mesoporous carbon exhibits efficient catalytic activity for the electrochemical hydrogen evolution reaction, with an overpotential of only 65 mV at a current density of 100 mA cm⁻² and long-time durability (>10 h), superior to state-of-the-art platinum/carbon. This iced-photochemical reduction may be extended to other single atoms, for example gold and silver, as demonstrated in this study.

Preparation of single atom catalysts (SACs) is of broad interest to materials scientists and chemists but remains a formidable challenge. Herein, we develop an efficient approach to synthesize SACs via a precursor-dilution strategy, in which metalloporphyrin (MTPP) with target metals are co-polymerized with diluents (tetraphenylporphyrin, TPP), followed by pyrolysis to N-doped porous carbon supported SACs (M₁/N-C). Twenty-four different SACs, including noble metals and non-noble metals, are successfully prepared. In addition, the synthesis of a series of catalysts with different surface atom densities, bi-metallic sites, and metal aggregation states are achieved. This approach shows remarkable adjustability and generality, providing sufficient freedom to design catalysts at atomic-scale and explore the unique catalytic properties of SACs. As an example, we show that the prepared Pt₁/N-C exhibits superior chemoselectivity and regioselectivity in hydrogenation. It only converts terminal alkynes to alkenes while keeping other reducible functional groups such as alkenyl, nitro group, and even internal alkyne intact.

Here we find the peculiar behavior of Cu ions in the PbSe–Cu system increases its thermoelectric performance. For the electrical transport, a dynamic doping effect is achieved because more Cu ions enter into the PbSe lattice and provide extra charge carriers as the temperature increases, which guarantees an optimized carrier concentration over a wide temperature range. For the thermal transport, the presence of Cu₂Se nanoprecipitates and dislocations at a low temperature range as well as the vibration of Cu atoms around the interstitial sites of PbSe at high temperatures result in hierarchical phonon scattering and a significantly reduced lattice thermal conductivity over the whole temperature range. As a result, a peak thermoelectric material figure of merit zT of up to 1.45 and a thermoelectric device figure of merit ZT close to unity are obtained for the sample with 0.375 at% Cu. Furthermore, enhanced thermoelectric properties are also realized for the Cu-intercalated PbS, implying that the temperature-driven dynamic behavior of Cu ions in a rigid lattice can serve as a general strategy to optimize the thermoelectric performance of IV–VI compounds.

The oxygen evolution reaction (OER) involving multi-step electron transfer is a challenging approach for water-splitting due to its sluggish kinetics. It is desirable to explore more efficient electro-catalysts with earth-abundant elements. Herein, we employed a high-temperature polymerization method to develop a structure consisting of graphitic carbon nitride (g-C₃N₄) nanopatch enveloped carbon nanotubes (CNTs), where isolated Ni and Fe atoms were embedded into the tri-s-triazine units of g-C₃N₄ by forming a metal–N_x structure. The designed dual-metal catalyst exhibited remarkable OER performance with an extremely low overpotential (∼326 mV at 10 mA cm⁻²) and a small Tafel slope (67 mV per decade), which is superior to those of state-of-the-art electrocatalysts with metal–N_x coordination and the benchmark IrO₂/C catalyst. In combination with atomic microscopy observations, our synchrotron-based X-ray absorption spectroscopy results revealed that, as compared to single-metal (Fe or Ni) doped hybrids, the electronic structures of both Ni and Fe atoms were reconfigured in the obtained dual-metal samples. Notably, increase of the oxidative state in Ni sites after multi-metal doping directly contributed to more active sites and favored the OER process, assisted by the porous structure and good electrical contacts between CNTs and g-C₃N₄. This investigation clearly demonstrated a unique synergistic effect in atomically dual-metal doped catalysts, thus it may provide a versatile route to regulate the electronic structures of single atomic catalysts through engineering of neighboring elements and coordination number.