Pore Size Effects of Mesoporous N‐Doped Carbon Nanospheres as Advanced Support Material on the Activity of Molybdenum Sulfide Catalysts for the Hydrogen Evolution Reaction

ABSTRACT Hydrogen is a key sustainable chemical energy carrier due to its high gravimetric energy density (143 MJ kg − 1 , higher heating value (HHV)). It can be generated from electrochemical water splitting powered by renewable energy, but requires active and stable electrocatalysts. Hereby, platinum, the benchmark catalyst, is scarce and expensive, limiting the feasibility of affordable green hydrogen. In contrast, molybdenum sulfide (MoS x ) offers a promising alternative due to its reasonable activity, abundance, low cost, and chemical stability. Increasing the catalytic activity of MoS x can be achieved by increasing active sites, doping, or using conductive supports. We report MoS x catalysts immobilized on mesoporous nitrogen‐doped carbon (MPNC) nanospheres as advanced supports. The high surface area and uniformity of MPNC enable thin, homogeneous MoS x coatings. After optimizing MoS x loading (38 wt.%) and MoS x precursor decomposition temperature (80°C), we tuned MPNC intraparticle pore sizes from 15 to 99 nm. A pore size of 60 nm yielded the best hydrogen evolution performance. This catalyst showed an onset potential of −155 mV vs. RHE and achieved 10 mA cm − 2 at −199 mV. Electrochemical mass spectrometry confirmed hydrogen generation already from −110 mV vs. RHE. A low Tafel slope of 44 mV dec − 1 highlights the composite's promise for high current density hydrogen evolution.