A cocatalyst plays an essential role in photoassisted hydrogen generation, and it is an almost inevitable component of a photocatalyst. Costly noble metal (e.g., Pt) cocatalysts exhibit almost irreplaceable efficiencies, and finding a suitable replacement is a challenging proposition. Controlled synthesis of a nanoparticle cocatalyst on semiconductors at the nanoscale level is one of the most promising approaches to accomplish the Pt equivalent activity. Herein, a photodeposited metallic Ni-based cocatalyst containing a small amount of Pt (<2 atom % with respect to Ni) on reduced/black TiO 2−x is introduced. The developed cocatalyst (2.21 wt % Ni and 0.094 wt % Pt with respect to TiO 2−x ) exhibits better charge separation efficiency and photoassisted hydrogen generation rate than an only-Pt (0.91 wt %) cocatalyst from methanol−water. The rates are 69 and 3.1 mmol g −1 h −1 for a Ni-based cocatalyst, while 65 and 2.5 mmol g −1 h −1 for a Pt cocatalyst, respectively, under ultraviolet−visible and visible light. A small amount of Pt ensures the photodeposition of Ni nanoparticles adjacent to Pt nanoparticles, enhancing the charge migration from the reduced TiO 2−x surface for hydrogen evolution. It is found that in the absence of Pt, the photodeposited Ni(OH) 2 is obtained instead of metallic Ni nanoparticles, which exhibits a comparatively low hydrogen generation rate. The present study opens an alternative way to cocatalyst design and fabrication by the controlled synthesis of nanoparticles for a wide range of photocatalytic conversions facilitated by enhanced charge separation.

Carbon deposition on a catalyst surface is detrimental to the dry reforming of methane (DRM) reaction. The addition of boron (B) is found to be effective in lowering carbon deposition. In this study, bimetallic Ni, Co catalysts over MgAl 2 O 4 (MA) [B−(Ni−Co)/ MA] with different Ni/Co ratios are synthesized by the NaBH 4 reduction method and examined for DRM at 600 °C and atmospheric pressure. The NaBH 4 plays crucial roles in reducing metal salt to metal, incorporating B, and enhancing the dispersion of active metallic species in a one-step catalyst preparation method. Rod-like Ni−Co alloy and B−(Ni−Co) nanostructures on the two-dimensional flakes of MA are observed. The Ni-rich B-containing bimetallic [B−(75Ni−25Co)] catalyst exhibits better methane and carbon dioxide conversions compared to other prepared catalysts. The turnover frequency (CH 4 ) and produced syngas ratio of the B-catalyst are 1.5 and 1.04 times, respectively, higher than the non-B catalyst prepared by the traditional impregnation method with the same Ni/Co ratio. The catalyst [B− (75Ni−25Co)] exhibits higher activity and almost a steady conversion rate, while continuous decrement is observed for the non-B catalyst. Exceptionally low carbon deposition (∼3.6 times) was observed for B−(75Ni−25Co)/ MA than the non-B catalyst. Furthermore, the density functional theory investigation also revealed that the adsorption energy (E ads ) of carbon at various sites of 75Ni25Co significantly reduces by ∼0.5 eV in the presence of B, causing hindrance to the formation of carbon over the surface.

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