Because of the interesting activities and relatively high stability, Bi2WO6 photocatalyst has been widely investigated. Several strategies have been proven effective in improving its performance. Here, we investigate the enhancement...

Phosphorus (P)-doped BiVO4 has been proposed as a promising photoanode for water splitting as it exhibits significant improvement of photocurrent density and photocatalytic O2 evolution rate. Previous findings suggest that substitution of V with P induces lattice polarization, which facilitates electron–hole separation. However, little attention has been paid to the mechanism underlying the observed changes in electronic conductivity due to oxygen vacancies. In this work, we carry out first-principles calculations to study the effect of P doping on the stability of oxygen vacancies and charge transport properties of BiVO4 photocatalysts. Our computations reveal improved reducibility of P-doped BiVO4 as reflected in the lower energies of oxygen vacancy formation. The generated oxygen vacancy yields two electron polarons localized at the two nearest V centers, where one polaron is always trapped at the defect site. The calculated polaron hopping barriers and their mobilities obtained from kinetic Monte Carlo simulations indicate that the P impurity by itself does not significantly alter the behavior of polaron transport. Hence, P doping improves reducibility of the material, which, in turn, increases the number of charge carriers and improves the electronic conductivity, which could lead to superior photocatalytic activity. These results can explain the experimentally observed higher concentration of oxygen vacancies and the enhancement of photocurrent density of P-doped BiVO4. This study provides valuable insights for designing doping strategies to improve the photocurrent density of photocatalysts.

Electron−hole recombination is one of the major issues inhibiting practical use of photocatalysts for water splitting to generate clean hydrogen energy. Engineering a heterostructure with an S-scheme heterojunction has been reported to promote e−h separation and maximize potential of photogenerated charge carriers, which, in turn, dramatically improve photocatalytic activity. Herein, based on density functional calculations, we proposed a design of a 2D/2D g-C 3 N 4 /ZnO heterostructure to achieve an S-scheme heterojunction with high catalytic activity toward the overall water splitting reaction. We find that the heterostructure constructed from high tensile strain of the ZnO monolayer and the equilibrium g-C 3 N 4 monolayer exhibits an S-scheme heterojunction. The built-in electric field generated at the interface effectively separates electrons to locate at the g-C 3 N 4 side and holes at the ZnO side leading to lower e−h recombination. The heterostructure improves sunlight utilization where its absorption edge is red-shifted into the visible-light region with a higher absorption coefficient when compared to that of individual monolayers. In addition, the mechanistic study reveals that potential of holes at the valence band of the ZnO side can overcome the potential limiting step of the oxygen evolution reaction, while the hydrogen evolution reaction prefers to occur at the g-C 3 N 4 side, which is also where the electrons are accumulated. Our study demonstrates how we can rationally design high-performance 2D/2D heterostructure photocatalysts for overall water splitting based on first-principles modeling.

The structure–activity relationship is a cornerstone topic in catalysis, which lays the foundation for the design and functionalization of catalytic materials. Of particular interest is the catalysis of the hydrogen evolution reaction (HER) by palladium (Pd), which is envisioned to play a major role in realizing a hydrogen‐based economy. Interestingly, experimentalists observed excess heat generation in such systems, which became known as the debated “cold fusion” phenomenon. Despite the considerable attention on this report, more fundamental knowledge, such as the impact of the formation of bulk Pd hydrides on the nature of active sites and the HER activity, remains largely unexplored. In this work, classical electrochemical experiments performed on model Pd(hkl) surfaces, “noise” electrochemical scanning tunneling microscopy (n‐EC‐STM), and density functional theory are combined to elucidate the nature of active sites for the HER. Results reveal an activity trend following Pd(111) > Pd(110) > Pd(100) and that the formation of subsurface hydride layers causes morphological changes and strain, which affect the HER activity and the nature of active sites. These findings provide significant insights into the role of subsurface hydride formation on the structure–activity relations toward the design of efficient Pd‐based nanocatalysts for the HER.