Hydrogen peroxide (H2O2) is a commodity chemical that serves as an oxidant and disinfectant for a number of historically important chemical end-use applications. Its synthesis can be made more sustainable, clean, and geographically distributed through technology enabled by the aqueous electrocatalytic two-electron reduction of O2, which produces H2O2 using only air, water, and electricity as inputs. Herein results are presented establishing that Pd, which is widely known to catalyze the four-electron reduction of O2 to H2O, can be made highly selective toward H2O2 production when it is deposited in situthat is, through electrochemical deposition from Pd ions during O2 reduction. The resultant cathodes are found to be comprised of sub-5 nm amorphous Pd nanoparticles and are measured to facilitate H2O2 selectivities above 95% in the relevant potential range. In addition, the cathodes are highly activethey are associated with the second-highest partial kinetic current density for H2O2 production in acidic media reported in the known literature. It is observed that in situ synthesis of Pd catalysts enables dramatic gains in H2O2 yield for all inert, conductive supports studied (including glassy carbon, commercial activated carbon, graphene, and antimony-doped tin oxide). Further efforts to generalize these results to other systems establish that even Pt, the prototypical four-electron O2 reduction catalyst, can be engineered to be highly selective to H2O2 when it is synthesized in situ under relevant conditions. These results and the comprehensive electrochemical and physical characterization presented, including synchrotron-based X-ray absorption spectroscopy, suggest that in situ synthesis is a promising approach to engineer O2 reduction electrocatalysts with tunable product selectivity and activity.

Semiconductor photocatalysts are hardly employed for overall water splitting beyond 700 nm, which is due to both thermodynamic aspects and activation barriers. Metallic materials as photocatalysts are known to overcome this limitation through interband transitions for creating electron-hole pairs; however, the application of metallic photocatalysts for overall water splitting has never been fulfilled. Black tungsten nitride is now employed as a metallic photocatalyst for overall water splitting at wavelengths of up to 765 nm. Experimental and theoretical results together confirm that metallic properties play a substantial role in exhibiting photocatalytic activity under red-light irradiation for tungsten nitride. This work represents the first red-light responsive photocatalyst for overall water splitting, and may open a promising venue in searching of metallic materials as efficient photocatalysts for solar energy utilization.

The atomically controlled transition of nanohybrids and their effects on charge-carrier dynamics are highly desirable for fundamental studies in photocatalysis. Herein, for the first time, a method combining atomic monodispersity and single-atom alloy was used to prepare a new form of highly efficient silver-based cocatalysts (Ag & PtAg) on graphitic carbon nitride, representing a novel photocatalytic system for hydrogen evolution.

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Porous oxygen-doped graphitic carbon nitride (g-CN) with feeble nitrogen vacancies was fabricated through thermal polycondensation of melamine with an appropriate amount of polyvinylpyrrolidone. After optimization, the bandgap of g-CN can be narrowed by 0.2 eV and the specific surface area expanded, which contribute to increasing the utilization of solar energy. Consequently, the optimized g-CN exhibits impressive enhancement in photocatalytic hydrogen evolution performance, by nearly 5 times compared with the pristine one under the irradiation of visible light.