Catalyst design and structure control for photocatalytic refineries of cellulosic biomass to fuels and chemicals

Lignocellulosic biomass is the largest renewable hydrocarbon resource on earth. Converting cellulose, one of the major components of lignocellulose, powered by solar energy is a promising way of providing low-carbon-footprint energy chemicals such as H2, HCOOH, CO, and transportation fuels. State-of-the-art biorefineries target the full use of biomass feedstocks as they have a maximum collection radius of 75-100 km, requesting efficient and selective photocatalysts that significantly influence the outcome of photocatalytic biorefineries. Well-performed photocatalysts can harvest a broad solar spectrum and are active in breaking the chemical bonds of cellulose, decreasing the capital investments of biorefineries. Besides, photocatalysts should control the selectivity of cellulose conversion, originating target products to level down separation costs. Charge separation in photocatalysts and interfacial charge transfer between photocatalysts and cellulose affect the activity and selectivity of cellulose refineries to H2 and carbonaceous chemicals. To account for the challenges above, this review summarizes photocatalysts for the refineries of cellulose and downstream platform molecules based on the types of products, with the structure features of different types of photocatalysts discussed in relation to the targets of either improving the activity or product selectivity. In addition, this review also sheds light on the methods for designing and regulating photocatalyst structures to facilitate photocatalytic refineries of cellulose and platform molecules, meanwhile summarizing proposed future research challenges and opportunities for designing efficient photocatalysts.