Oxygen vacancies (OVs) have emerged as an important strategy to modulate the electronic structures, conductivity, and catalytic performance of transition metal oxides (TMOs). A few studies reported that OVs could be formed in N-doped TMOs during ammonia treatment. However, the OV-enriched TMOs without N-doping obtained through ammonia treatment are still unreported and their mechanism is unclear. Herein, we adopt experimental and theoretical investigations to demonstrate the mechanism of ammonia treatment. Based on this mechanism, we develop a facile method to synthesize OV-enriched blue WO 3Àx porous nanorods (OBWPN) without N-doping. OBWPN exhibit promising performance for photothermal reduction of CO 2 -H 2 O to CH 4 without any external cocatalysts or sacrificial agents. In addition, the low-temperature ammonia-assisted reduction treatment is a universal strategy to generate OVs in other TMOs with enhanced performance of photocatalytic hydrogen generation. This work is significant for understanding the nature of ammonia treatment and promoting the wide application of OV-enriched TMOs.

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Automotive exhaust emission is a major cause of air pollution. Three-way catalyst (TWC) which can eliminate CO, HC (hydrocarbons), and NO(x) simultaneously has been used to control exhaust emissions. Ceria-zirconia is a key component in TWC and most researchers pay attention to Ceria-Zirconia (Ce-rich) solid solution. The research presented in this paper is focused on the intrinsic structure of Ceria-Zirconia (Zr-based) solid solution and its application in TWC. A series of Ce(0.2)Zr(0.8)O(2) modified with rare earths (La, Nd, Pr, Sm, and Y) have been prepared by coprecipitation method combined with supercritical drying technique. All samples showed single tetragonal solid solution, indicating that the rare earth ion inserted into the lattice structure completely, and an approximately linearly relationship between lattice parameter a and the ionic radius of doped rare earth was observed. The catalytic performances of corresponding Pd-only catalysts were investigated in simulated exhaust gas. The presence of La, Nd, and Pr was favorable to the catalytic activity and wide air/fuel operation window. The relationship between the intrinsic structure of the Zr-based ceria-zirconia solid solution and catalytic activity was discussed in detail, which has some reference value for catalyst design and application.