Photocatalytic Hydrogen Production: A Rift into the Future Energy Supply

Abstract

Photocatalytic hydrogen (H2) production is a process that converts solar energy into chemical energy by means of a suitable photocatalyst. After the huge amount of systems that have been tested in the last forty years, the advent of nanotechnology and a careful design at molecular level, allow to obtain attractive activity, even using pure visible light. At the same time we are approaching reasonable photocatalyst stability in laboratory test, and the attention is paid to identify cost-effective photocatalysts that might find real applications. This Review provides a broad overview of the elementary steps of the heterogeneous photocatalytic H2 production, including an outline of the physico-chemical reactions occurring on semiconductors and cocatalysts. The use of different renewable oxygenates as sustainable sacrificial agent for the H2 production is outlined, in view of a transition from fossil fuels to pure water splitting. Finally, the recent advances in the development of photocatalyst are discussed focusing on the current progress in organic and hybrid organic/inorganic photocatalysts

Comprehensive review and future perspectives on the photocatalytic hydrogen production

“…The function of a high performance heterogeneous photocatalyst is to: (i) avoid fast electron–hole recombination; (ii) allow fast diffusion of the electrons and holes to the surface of the semiconductor; (iii) have band potentials suitable to those of the sacrificial agent oxidation and proton reduction; (iv) be photoactive under visible light, which is related to the band gap of the semiconductor; (v) to display good chemical stability; and (vi) to be cost‐effective …”

“…Moreover, the metal can improve the light absorption by surface plasmon resonance. The use of noble metals as co‐catalysts provides higher H 2 production rates than the semiconductor catalyst alone; however, their associated high cost, and scarce availability limit their application . The third strategy consists of coupling two semiconductors.…”

Apparent Potential Difference Boosting Directional Electron Transfer for Full Solar Spectrum‐Irradiated Catalytic H2 Evolution

“…Hydrogen is considered as a clean and green energy benefitting from water as its only combustion product with high calorific value of 122 kJ kg −1 . Among the strategies for H 2 production, photocatalytic H 2 O splitting into H 2 is confirmed to be a promising alternative through solar energy conversion over semiconductors .…”

A Kinetic Model of Photocatalytic Hydrogen Production Employing a Hole Scavenger

“…In the search for new energy sources, with a higher heating value than that of fossil fuels and lower emission of pollutants, hydrogen has emerged as an abundant, sustainable, environmentally friendly fuel , . Hydrogen can be produced from diverse resources, including fossil fuels, biomass, and water, through electrolytic or photocatalytic means .…”