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The CO2 hydrogenation (HYD) reaction was investigated over Ni phosphide (Ni3P, Ni12P5, Ni2P) catalysts to probe the effect of the NixPy phase on photo-thermal catalytic properties in comparison to Ni metal. The light absorption properties of 2.5 wt% NixPy/SiO2 catalysts differ substantially, with the extent of light absorption decreasing as the P/Ni molar ratio of the Ni phosphide phase increases. This finding directly impacts the photo-thermal catalytic properties as the photo-enhancement (light activity / dark activity) correlates linearly with the extent of light absorption. For comparison purposes, 2.5 wt% Ni/SiO2 catalysts were also investigated and showed high activity but suffered from low CO selectivity (57-68%). A Ni3P/SiO2 catalyst was the most active of the Ni phosphides with high CO selectivity (>95%), while Ni12P5/SiO2 and Ni2P/SiO2 catalysts had lower CO2 HYD activities but CO selectivities above 98%. Upon light exposure, the NixPy/SiO2 (and Ni/SiO2) catalysts exhibited significant rises of temperature (~200 K increase from room temperature), indicating the importance of photothermal heating in increasing the CO2 HYD rate. The findings highlight how a non-metal element (i.e., P) plays a crucial role in tailoring the photo-thermal catalytic properties of earth abundant nickel metal.