Controlled shifting of the CO ₂ reduction product from C ₁ to C ₂ hydrocarbons obtained with graphene wrapped blue titania under solar light.

Photocatalytic CO₂ conversion to fuel offers an exciting prospect for solar energy storage and transportation thereof. Several photocatalysts have been employed for CO₂ photoreduction; the challenge of realizing a low-cost, readily synthesized photocorrosion-stable photocatalytic material that absorbs and successfully utilizes a broad portion of the solar spectrum energy is as yet unmet. Herein, a mesoporous p-type/n-type heterojunction material, Cu_xO–TiO₂ (x = 1, 2), is synthesized via annealing of Cu/Cu₂O nanocomposites mixed with a TiO₂ precursor (TiCl₄). Such an experimental approach in which two materials of diverse bandgaps are coupled provides a simultaneous opportunity for greater light absorption and rapid charge separation because of the intrinsic p–n heterojunction nature of the material. As detailed herein, this heterostructured photocatalyst demonstrates an improved photocatalytic activity. With the CO₂ reduction of our optimal sample (augmented light absorption, efficacious charge separation, and mesoporosity) that utilizes no metal cocatalysts, a remarkable methane yield of 221.63 ppm·g⁻¹·h⁻¹ is achieved.

Cu–Pt bimetallic nanoparticles deposited over blue titania exhibiting record photoconversion efficiency for CO ₂ photoreduction into fuels.

Photocatalytic CO₂ reduction is emerging as an affordable route for abating its ever increasing concentration. For commercial scale applications, many constraints are still required to be addressed. A variety of research areas are explored, such as development of photocatalysts and photoreactors, reaction parameters and conditions, to resolve these bottlenecks. In general, the photocatalyst performance is mostly adjudged in terms of its ability to only produce hydrocarbon products, and other vital parameters such as light source, reaction parameters, and type of photoreactors used are not normally given appropriate attention. This makes a comprehensive comparison of photocatalytic performance quite unrealistic. Hence, probing the photocatalytic performance in terms of apparent quantum yield (AQY) with the consideration of certain process and experimental parameters is a more reasonable and prudent approach. The present brief review portrays the importance and impact of aforementioned parameters in the field of gas phase photocatalytic CO₂ reduction.

Practical implementation of CO₂ photoreduction technologies requires low-cost, highly efficient, and robust photocatalysts. High surface area photocatalysts are notable in that they offer abundant active sites and enhanced light harvesting. Here we summarize the progress in CO₂ photoreduction with respect to synthesis and application of hierarchical nanostructured photocatalysts.