We report the photocatalytic conversion of CO₂ to CH₄ using CuPt alloy nanoclusters anchored on TiO₂. As the size of CuPt alloy nanoclusters decreases, the photocatalytic activity improves significantly. Small CuPt nanoclusters strongly bind CO₂ intermediates and have a stronger interaction with the TiO₂ support, which also contributes to an increased CH₄ generation rate. The alloying and size effects prove to be the key to efficient CO₂ reduction, highlighting a strategic platform for the design of photocatalysts for CO₂ conversion.

Hydrogen has received substantial attention because of its diverse application in the energy sector. Steam methane reforming (SMR) dominates the current hydrogen production and is the least expensive endothermic reaction to produce grey hydrogen. This technology provides the advantages of low cost and high energy efficiency; however, it emits an enormous amount of CO₂. Carbon capture storage (CCS) technology helps reduce these emissions by 47% to 53%, producing blue hydrogen. Methane pyrolysis is an alternative to SMR that produces (ideally) CO₂-free turquoise hydrogen. In practice, methane pyrolysis reduces CO₂ emissions by 71% compared to grey hydrogen and 46% compared to blue hydrogen. While carbon dioxide emissions decrease with CCS, fugitive methane emissions (FMEs) for blue and turquoise hydrogen are higher than those for grey hydrogen because of the increased use of natural gas to power carbon capture. We undertake FMEs of 3.6% of natural gas consumption for individual processes. In this study, we also explore the utilization of biogas as a feedstock and additional Boudouard reactions for efficient utilization of solid carbon from methane pyrolysis and carbon dioxide from biogas. The present study focuses on possible ways to reduce overall emissions from turquoise hydrogen to provide solutions for a sustainable low-CO₂ energy source.