Cocatalyst plays a critical role in photocatalytic overall water splitting (POWS). However, the typical metal cocatalysts aimed at promoting hydrogen evolution are also highly active for H₂-O₂ recombination. Here we report a new strategic approach of coating single-layer graphene selectively on metal cocatalyst by chemical vapor deposition to effectively suppress the backward reaction for efficient POWS. Pt@C/SrTiO₃ demonstrates steady POWS activity in contrast to the rapid activity decline by 65% in 5 h of Pt/SrTiO₃, and no obvious H₂ and O₂ consumption is observed over Pt@C/SrTiO₃ during dark reaction. Experimental and theoretical calculation results indicate that the graphene prevents O₂ from contacting Pt and the O₂ dissociation as the rate-determining step of backward reaction is retarded. Moreover, this method demonstrates good universality and similar suppressing effect is also achieved over Rh, Pd@C. These findings may open a new pathway for developing effective cocatalysts with suppressed backward reaction for efficient POWS.

助催化剂在光催化全水分解 (POWS) 中起着关键作用。然而，旨在促进析氢的典型金属助催化剂对于H ₂ -O ₂重组也具有高活性。在这里，我们报告了一种新的战略方法，通过化学气相沉积在金属助催化剂上选择性地涂覆单层石墨烯，以有效抑制高效 POWS 的逆向反应。Pt@C/SrTiO _{3表现出稳定的 POWS 活性，而 Pt/SrTiO 3}的活性在 5 小时内迅速下降 65% ，并且在 Pt@C/SrTiO ₃上没有观察到明显的 H ₂和 O ₂消耗暗反应时。实验和理论计算结果表明，石墨烯阻止了O ₂与Pt的接触和O ₂解离，因为逆向反应的决速步骤被延迟了。此外，该方法具有良好的普适性，在 Rh、Pd@C 上也取得了类似的抑制效果。这些发现可能为开发有效助催化剂开辟一条新途径，抑制逆向反应以实现高效 POWS。