Atomic-level insight into the unique catalytic capability of single-atom catalysts that distinguished from nanometer-sized counterparts is highly desirable for catalyst design and catalysis research. By synthesizing single Pd atoms supported on TiO₂ as a catalyst, here we demonstrate a steric hindrance effect of single atoms induced by the unique isolation of single-atom active sites to achieve a remarkable enhancement on catalytic performance in the synthesis of dimethyl carbonate. Experimental results and density functional theory calculations reveal that such steric hindrance effect of single atoms favors the yield of the desired product dimethyl carbonate against further reacting with intermediates to form byproduct, because no extra Pd species around single Pd atoms provide active sites to further adsorb and activate substrates directly. The discovery of such steric hindrance effect is a valuable supplement to single-atom catalysis, and may promote single-atom catalysts to be widely applied in selective catalytic reactions.

对于催化剂设计和催化研究，非常需要对单原子催化剂的独特催化能力进行原子级洞察，以区别于纳米尺寸的催化剂。通过合成负载在 TiO ₂上的单个 Pd 原子作为催化剂，我们在这里展示了由单原子活性位点的独特隔离引起的单原子的空间位阻效应，从而显着提高了合成碳酸二甲酯的催化性能。实验结果和密度泛函理论计算表明，单原子的这种位阻效应有利于目标产物碳酸二甲酯的产率，不会与中间体进一步反应形成副产物，因为单个 Pd 原子周围没有额外的 Pd 物质提供活性位点以进一步吸附和直接激活底物。这种位阻效应的发现是对单原子催化的一个有价值的补充，可能会促进单原子催化剂在选择性催化反应中的广泛应用。