The water–gas shift (WGS) reaction is an industrially important source of pure hydrogen (H₂) at the expense of carbon monoxide and water^1,2. This reaction is of interest for fuel-cell applications, but requires WGS catalysts that are durable and highly active at low temperatures³. Here we demonstrate that the structure (Pt₁–Pt_n)/α-MoC, where isolated platinum atoms (Pt₁) and subnanometre platinum clusters (Pt_n) are stabilized on α-molybdenum carbide (α-MoC), catalyses the WGS reaction even at 313 kelvin, with a hydrogen-production pathway involving direct carbon monoxide dissociation identified. We find that it is critical to crowd the α-MoC surface with Pt₁ and Pt_n species, which prevents oxidation of the support that would cause catalyst deactivation, as seen with gold/α-MoC (ref. ⁴), and gives our system high stability and a high metal-normalized turnover number of 4,300,000 moles of hydrogen per mole of platinum. We anticipate that the strategy demonstrated here will be pivotal for the design of highly active and stable catalysts for effective activation of important molecules such as water and carbon monoxide for energy production.

水煤气变换 (WGS) 反应是工业上重要的纯氢 (H ₂ ) 来源，但会消耗一氧化碳和水^1,2。这种反应对燃料电池应用很感兴趣，但需要在低温下耐用且高活性的 WGS 催化剂³。在这里，我们证明了结构 (Pt ₁ –Pt _n )/α-MoC，其中孤立的铂原子 (Pt ₁ ) 和亚纳米级铂簇 (Pt _n ) 稳定在 α-碳化钼 (α-MoC) 上，催化 WGS甚至在 313 开尔文的温度下也发生反应，确定了涉及直接一氧化碳解离的制氢途径。我们发现用 Pt 填充 α-MoC 表面是至关重要的₁和 Pt _n物质，可防止载体氧化导致催化剂失活，如金/α-MoC（参考文献⁴）所示，并赋予我们的系统高稳定性和 4,300,000 摩尔的高金属归一化周转数每摩尔铂的氢。我们预计，这里展示的策略对于设计高活性和稳定的催化剂至关重要，以有效激活水和一氧化碳等重要分子以产生能源。