Full-Spectrum Light-Harvesting Solar Thermal Electrocatalyst Boosts Oxygen Evolution.

Enabling high-efficiency solar thermal conversion (STC) at catalytic active site is critical but challenging for harnessing solar energy to boost catalytic reactions. Herein, we report the direct integration of full-spectrum STC and high electrocatalytic oxygen evolution activity by fabricating a hierarchical nanocage architecture composed of graphene-encapsulated CoNi nanoparticle. This catalyst exhibits a near-complete 98 % absorptivity of solar spectrum and a high STC efficiency of 97 %, which is superior than previous solar thermal catalytic materials. It delivers a remarkable potential decrease of over 240 mV at various current densities for electrocatalytic oxygen evolution under solar illumination, which is practically unachievable via traditionally heating the system. The high-efficiency STC is enabled by a synergy between the regulated electronic structure of graphene via CoNi-carbon interaction and the multiple absorption of lights by the light-trapping nanocage. Theoretical calculations suggest that high temperature-induced vibrational free energy gain promotes the potential-limiting *O to *OOH step, which decreases the overpotential for oxygen evolution.